2016 Vol. 33, No. 2

Display Method:
2016, 33(2)
Synthesis and Performance Evaluation of Bio-mass Synthetic Base Fluid LAE-12
SHAN Haixia, WANG Zhonghua, HE Huanjie, SUN Ju, GUO Minle, LIU Minghua, XU Qin
2016, 33(2): 1-4. doi: 10.3969/j.issn.1001-5620.2016.02.001
Biomass synthetic base drilling fluid has been regarded as an environmentally friendly substitute for oil base drilling fluid.A base fluid for the biomass drilling fluid,LAE-12,a lauryl ether,has recently been developed through one-step synthesis using lauryl alcohol as raw material.Studies on the basic physio-chemical properties,viscosity characteristics and anti-hydrolysis performance of LAE-12 are conducted and comparisons of LAE-12 and other base fluids such as diesel oil,white oil and bio-diesel oil are done.The flash point,pour point,boiling point and extreme-pressure friction coefficient of LAE-12 are 137℃,-13℃,289℃,and 0.039,respectively,meaning that the safety and lubrication performances of LAE-12 are better than those of diesel oil and white oil.Changes of the viscosity of LAE-12 with temperature between 0℃ and 90℃ are much more gently than diesel oil and white oil,and are comparable to bio-diesel oil.In water with pH value of 12,LAE-12 is resistant to hydrolysis,while 72% of bio-diesel oil is hydrolyzed.Oil base drilling fluids formulated with LAE-12(O/W ratio=8:2) have emulsion stability of greater than 600 V,YP/PV of greater than 0.30 Pa/mPa·s,and stable rheology after ageing for 64 h at 150℃.In laboratory testing,the LAE-12 base drilling fluid has performance that is equivalent to oil base drilling fluid.
Study on High Temperature Salt-resistant Viscosifier and the Formulated Solids-free Drilling Fluid
LIU Jianjun, LIU Xiaodong, MA Xueqin, ZHU Hongwei
2016, 33(2): 5-11. doi: 10.3969/j.issn.1001-5620.2016.02.002
A high temperature salt-resistant viscosifier,BDV-200S,has been developed from 2-Acrylamido-2-methylpropane sulfonic acid (AMPS),acryl amide (AM) and another monomer X.Studies have been conducted on the molecular structures,molecular weights and distributions,and the thermal stability of BDV-200S molecules.Rheology and functioning stability at elevated temperatures were studied through high temperature rheological measurement,ratio of viscosity retention after aging at high temperature,suspension of barite in the aged muds treated with BDV-200S,and bottom-hole dynamic circulation simulation test etc.The performances of BDV-200S in solid-free drilling fluids at 120℃,150℃,and 180℃ were compared with those of the similar products.These studies reveal that the BDV-200S synthesized is the product designed.BDV-200S has a weight average molecular weight of about 2,000,000 which is distributed in a narrow range.After aging at 180℃ for 16 h,the BDV-200S solution still retained viscosity of greater than 45% of its original viscosity,and the color of the solution was still white.No barite settlement has been found of the solution,meaning that the suspending capacity of BDV-200S is satisfactory.A laboratory test simulating mud circulation in hole with bottom hole temperature of 180℃ indicated that the solution,after 4 cycles of circulation,still retained viscosity more than 50% of its original viscosity.In salt resistant performance testing,the viscosity of the saltwater increased with the concentration of BDV-200S in a linear relationship.Drilling fluids treated with BDV-200S has API filter loss of 5.0 mL,and HTHP filter loss of 19 mL at 150℃.The evaluation reveals that BDV-200S possesses a better performance than other similar products.
Synthesis and Evaluation of High Temperature Weak Gel Viscosifier WG-1
SUN Ju, LI Zhenzhi, SU Xuexia, ZHENG Zhijun, SONG Yajing
2016, 33(2): 12-16. doi: 10.3969/j.issn.1001-5620.2016.02.003
A high temperature weak gel viscosifier WG-1 has been developed using inverse emulsion polymerization in an effort to satisfy the needs for high temperature deep wells and non-conventional wells.The optimum synthesis conditions were determined and key factors affecting the performance of WG-1 examined.Groups such as AMPS,DMAM and NVP are found in the molecular structure of WG-1 through SEM observation,and these groups are in spherical forms,with diameters between 0.1 μm and 1.8 μm.These data demonstrate that WG-1 has good thermal stability,salinity tolerance and superior thickening and gelling capacity.A 1.0% WG-1 solution,after aging at 200℃ for 16 h,had YP/PV ratio of 0.47 Pa/mPa·s,suitable for use at that temperature as a viscosifier and gelling agent.WG-1 solution retained enough viscosity and gel strengths after aging for 72 h at 170℃,meaning that it suffices the needs for operation at 170℃.WG-1 can be used in both fresh water and saltwater drilling fluids as viscosifier and filter loss reducer.After aging at 170℃,the filtration rate of fresh water base drilling fluid was reduced from 9.6 mL to 4.8 mL,and that of saturated water base drilling reduced from 8.8 mL to 3.2 mL,indicating that WG-1 can plug micro fractures and improve the quality of mud cakes,thereby reduce the filtration rate.
Synthesis and Evaluation of a High Temperature Inhibitive Additive
KONG Yong, YANG Xiaohua, XU Jiang, LIU Guichuan, WANG Haibo, ZHANG Guo
2016, 33(2): 17-21. doi: 10.3969/j.issn.1001-5620.2016.02.004
A high temperature inhibitive agent,FT-200 has recently been developed for use in high temperature deep well penetrating complex formations.FT-200 was developed through design of molecular structure,optimization of deformation and dispersion properties,and optimization of reaction raw materials and synthesis method.FT-200 deforms at high temperature and plugs micro fractures through elasticity.It improves the strengths of unstable formations through cementation.Characterization of FT-200 through IR spectrum,NMR spectrometry,elementary analysis and TGA reveals that FT-200 has excellent high temperature property,fulfilling the design objective.Evaluation of the performance of FT-200 in drilling fluids indicates that FT-200 functions normally at temperature up to 200℃,and shales treated with FT-200 drilling fluid have their permeability reduced by more than 70%.The quality of mud cakes is improved by FT-200,and HTHP filter loss can be reduced remarkably using FT-200.FT-200 is compatible with commonly used drilling fluid additives,and it effectively seals off the micro fractures found in hard-brittle shales.
Synthesis and Evaluation of High Temperature Water Base Drilling Fluid Filter Loss Reducer
WANG Leilei, WANG Weizhong, ZHANG Kun, XU Haoran, HUANG Lin, GUO Jianmei, SONG Xuewen, WANG Qiang
2016, 33(2): 22-25. doi: 10.3969/j.issn.1001-5620.2016.02.005
Malfunction of filter loss reducer at elevated temperatures and high salinity environments are difficult problems encountered in deep and ultra-deep well drilling.A high temperature water base drilling fluid filter loss reducer,JLS200,has been developed using acryl amide,2-acrylamide-2-methyl propane sulfonic acid,N-Vinyl pyrrolidone and N-isopropyl acrylamide as raw materials.JLS200,as indicated by laboratory evaluation,can be used at 200℃,or in saturated saltwater drilling fluids,without losing its filtration control capacity.KCl drilling fluids treated with JLS200 have low filtration rate and good rheology,the API filtration rate has been reduced from 12 mL to 3.2 mL after treatment of the fluids with 1% JLS200 and ageing at 200℃,while the HTHP filtration rate reduced from 54 mL to 15 mL.The viscosity and gel strengths do not change remarkably before and after the treatment.JLS200 as a high performance filter loss reducer will find its application in deep and ultra-deep well drilling.
Application of Fluorescence Microscope in Analysis of Spatial Structure of Mud Cakes
YAO Rugang, PENG Chunyao, ZHANG Zhenhua, DING Guangbo, LI Shumin
2016, 33(2): 26-30. doi: 10.3969/j.issn.1001-5620.2016.02.006
The physicochemical structure of mud cake is the intrinsic factor controlling the quality of mud cakes,and fewer studies on the spatial distribution of the physicochemical structure of mud cakes have been conducted than the studies conducted on the surface microscopic morphology and element composition of mud cakes.A new method of studying the spatial distribution of the physicochemical structure of mud cakes using fluorescence microscope and the software Adobe Photoshop CS6 is presented.By measuring the pixels of the white (the original bluefluorescence) area and calculating their ratio,the concentration distribution of the tested additive in different layers of the mud cake can be seen directly.Using this method,a self-made compound (polymeric and nano) material,LX-2,was studied.The studies have demonstrated that the fluorescent area of polymers found in mud cakes takes on a spatial distribution of "surface layer >intermediate layer >bottom layer".The quantity of adsorbed water of mud cake measured with conventional drying method and polymer content in the mud cake measured with incineration method all take on a similar spatial distribution such as that just mentioned.It is believed that addition in drilling fluids of deformable additives that still retain strong hydration capacity and strong colloid-formation capacity,and effectively render mud cakes water-absorptivity at elevated temperatures,high pressures and high salinity conditions,will be an important way of enhancing the quality of mud cakes.This new method will help in further understanding the spatial distributioncharacteristicsof the physicochemical structure and its effects on the wall building capacity of drilling fluids,and this in turn,provides a new perspective and basis of improving the wall building capacity of drilling fluids.
Effects of Drilling Fluid Activity on Hydration and Dispersion of Formation Rocks in Shale Gas Drilling in Chuan-Dian Area
LIU Jingping, SUN Jinsheng
2016, 33(2): 31-35. doi: 10.3969/j.issn.1001-5620.2016.02.007
Reducing the activity ofthe filtrate of drilling fluid is an important technology in mitigating shale problems during drilling.In shale gas drilling in the Chuan-Dian area,highly water sensitive clayey formations with fractures highly developed have been frequently encountered,necessitating the means of borehole wall stabilization.Linear swelling and hot rolling tests using a drilling fluid formulated with CaCl2,potassium formate and glyceryl alcohol as the activity agents,and shale samples from Longmaxi formation (Yibin,Sichuan) and Wufeng formation (Yibin,Sichuan) show that the activity of the drilling fluid has played a slight role in the hydration and dispersion of the shales,indicating that osmotic hydration of the shales is not the main cause for the shale formations to collapse.Surface hydration,capillary pressure as well as the micro fractures developed in the shale formations may have been causing the shale formation to collapse.
Solid-free Thermal Insulation Water Base Packer Fluid Technology for Deep Water Operation
ZHOU Shanshan, XU Mingbiao, YOU Fuchang, CHEN Kan, SONG Jianjian
2016, 33(2): 36-40. doi: 10.3969/j.issn.1001-5620.2016.02.008
Solid-free thermal insulation water base packer fluid is a water base fluid used in the annulus of oil and gas wells to minimize the heat loss in oil and gas pipes and thus inhibit waxing and formation of gas hydrate therein.Heat loss in oil and gas pipes can be achieved by reducing the coefficient of heat conductivity of the fluid flowing in the pipes,and by controlling the free convection taking place in the pipes.In laboratory studies,a polybasic alcohol,C4,is selected as a reagent to reduce the coefficient of heat conductivity.A biopolymer,MT,is chosen as a rheology modifier;it reduces the viscosity of the flowing fluid at high shearing rate,thus satisfying the needs for pumping the fluid.On the other hand,MT increases the viscosity the fluid at low shearing rate,thus minimizing the heat loss caused by free convection in the annulus.Using soluble salts,the density of the fluid flowing in the pipes can be adjusted between 0.9 g/cm3 and 1.2 g/cm3,thus satisfying the needs of reservoirs with different pressure coefficients.The studies reveal that the new solid-free thermal insulation water base packer fluid has low coefficient of heat conductivity,good thermal insulation performance,wide density range,and good stability over long period.Compared with oil base packer fluid and alcohol base packer fluid,this new packer fluid has better heat insulation performance and low preparation cost,and it is free of solids precipitation and poses no pollution to the environment.
Study on Performance of A New Oil Base Mud Lost Circulation Material
LI Hongmei, SHEN Feng, WU Jinqiao, LI Wei, MA Zhenfeng
2016, 33(2): 41-44. doi: 10.3969/j.issn.1001-5620.2016.02.009
Fractures are usually highly developed in shale formations,making the shale easily swelling and breaking.Mud loss is another problem frequently encountered in shale drilling.To ensure hole stability,oil base drilling fluids are usually used and the losses of these expensive drilling fluids mean severe economic loss.To prevent the loss of oil base drilling fluids,an organophilic high molecular weight resin lost circulation material,YDLJ-1,has been developed.It has been proved that the YDLJ-1 has good stiffness and deformability,making it easy for the YDLJ-1 to fill the fractures through which the mud is lost.The capability of the YDLJ-1 to absorb oil makes it expandable,and in 5 h the volume of the YDLJ-1 that has absorbed oil is 5 times of its original volume.After ageing at 150℃ for 30 days,YDLJ-1 still retains certain compressive strength and deformability.The compressive strength of YDLJ-1 is 20 times that of the other similar products.Breakthrough pressure in forward direction against the surface of YDLJ-1 is greater than 15 MPa,and in backward direction against the surface of YDLJ-1 0.9 MPa,satisfying the needs for mud loss control.YDLJ-1 has been used in drilling the lower part of the Shiqianfeng formation penetrated by the Well Yunyeping-1 in Yanchang oilfield.2 ton of YDLJ-1 was used and the volume of mud loss was 30 m3 less than the offset well,time spent controlling the mud loss was shortened by 2 days,proving the efficiency of YDLJ-1 in mud loss control.
Preparation and Evaluation of New Borehole Wall Strengthening Agent
ZHANG Wei, MIAO Hailong, DENG Yicheng, XUE Kaihua
2016, 33(2): 45-49. doi: 10.3969/j.issn.1001-5620.2016.02.010
Thief zones frequently encountered in offshore drilling often negatively affect drilling speed and do harm to reservoirs.A bore hole strengthening agent,ENPRES-Seal has been developed to enhance the strengths to bear higher pressures that the formationscannot stand before strengthened by ENPRES-Seal.ENPRES-Seal is made of rigid particles,soft particles and deformable particles.Experiments on visual sand bed demonstrated that the mass ratio of the three particles is 2:1:2.Evaluation of ENPRES-Seal shows that the optimum concentration in drilling fluid is 2%-3%,and at this concentration it poses very small effect on the rheology of drilling fluid.ENPRES-Seal can be used at high temperatures as high as 200℃,and it does not blind shale shaker screen;85% of ENPRES-Seal passes 0.180 mm screen.ENPRES-Seal also renders drilling fluid good lubricity.The adsorption of ENPRES-Seal renders formation high compressive strength,as high as 17 MPa,and it also improves the quality of mud cake.ENPRES-Seal has been used on a HTHP well in Block Pinghunear Shanghai,where bottom hole temperature has been as high as 180℃,and mud density at well completion 1.90 g/cm3,and the strength of the borehole wall has been greatly enhanced.
Calcium Nitrate Treated Polyamine Drilling Fluid Technology
ZHENG Yuhui, JIANG Zhenwei, FAN Fan
2016, 33(2): 50-54. doi: 10.3969/j.issn.1001-5620.2016.02.011
In the marine sedimentary area in southeast Ecuador,formations drilled are young,unconsolidated,ready-to-disperse and highly mud making,especially theChalcanaand Orteguaza layers,where long sections of formations with more than 80% shales and with interbeded coal seams are found.These formations,having poor diagenetic grade and strong water absorption capacity,are very unstable and downhole troubles have long been encountered during drilling operations.A calcium nitrate treated polyamine drilling fluid has been engineered to drill these formations.This drilling fluid has stable properties and strong inhibitive capacity,and the rate of linear expansion of shale cores is only 0.47 mm after immersing 16 h in the drilling fluid,and the primary recovery of shale cuttings on hot rolling test is 96%,the secondary recovery of shale cuttings 88%.Tolerance to clay contamination is 6% and tolerance to cuttings contamination is 8%.This drilling fluid has low corrosion to drilling tools (corrosion rate is 0.058,5 mm/a),and is non-toxic and easy to degrade.Field application has demonstrated that this drilling fluid is highly inhibitive,has good hole cleaning capacity and cuttings carrying capacity.Good lubricity of the drilling fluid helped minimize bit balling.Borehole stabilization and safe drilling have been realized,and drilling time saved.The running of φ339.7 mm casing string has been completely successful.
Drilling Fluid Technology for ROP Enhancement in Slim Hole Drilling
LUO Gang, REN Kunfeng, XING Xijin, SHU Fuchang, XIANG Xingjin
2016, 33(2): 55-59. doi: 10.3969/j.issn.1001-5620.2016.02.012
Slim hole drilling,because of the narrow annulus,imposes more strict requirements on drilling engineering and drilling fluid.Drilling fluid plays an important role in fast drilling of slim holes.A drilling fluid formulation for slim hole drilling has been developed in laboratory,and drilling fluid additives suitable for slim hole drilling are engineered.These additives include viscosifier PLUS,flow pattern control agent,filter loss reducer HFL-X and SPNH,ROP enhancer HDS,and weighting material sodium formate used in combination with barite.HDS has been developed in laboratory for the preventing bit balling and reducing the content of submicron particles.HDS has good lubricity,inhibitive capacity and the ability to increase ROP.Field application has proved that this drilling fluid formulation controlled ECD fairly well and notably enhanced ROP,satisfying the needs for slim hole drilling.
Solids Control and Re-use of Water Base Drilling Fluid in Beibu Gulf
CHENG Yusheng, ZHANG Liquan, MO Tianming, XIANG Xiong, ZHANG Ming
2016, 33(2): 60-63. doi: 10.3969/j.issn.1001-5620.2016.02.013
Formation geology in the Beibu Gulf area is complex,making drilling operation very difficult.Solids control plays an important role in the success of drilling in this area.A complete set of solids control technology has been developed through laboratory analyses and experiments.The configuration and parameter specifications of solids control equipment (especially the selection of the screen cloth for shale shakers) are optimized through inspection of particle size distribution of the water drilling fluids.The treatment capacity,configuration and number of centrifuges are carefully determined to enhance the efficiency of solids control.In the treatment of the waste drilling fluids,the properties of the waste drilling fluids are firstly measured,then the waste drilling fluids are cleaned through the solids control equipment,and some new drilling fluids are prepared for use with the cleaned waste drilling fluids.In this way the properties of the drilling fluid satisfy the needs for the next hole section or the next well,and the mud cost,labor cost and transportation cost are all reduced.This technology has been successfully used on 29 wells in the Beibu Gulf area.
Application of Low Damage Drilling Fluid in Yibei Area
LI Xiuling, CHEN Erding, ZHANG Haiqing, WANG Jinli, WANG Zhi
2016, 33(2): 64-68. doi: 10.3969/j.issn.1001-5620.2016.02.014
A low damage drilling fluid has been developed to protect the low permeability reservoir in the Block 43,Yibei,Shengli oilfield.The development of the new drilling fluid is based on a "synergistic effect" of a drilling fluid for use in drilling low permeability reservoirs.AMP-2,a reservoir protection agent for the new drilling fluid,has strong plugging capacity and good stability;no settling has ever been found after standing for 30 days.FCS,a water blocking agent,does not settle at low temperature to -20℃.Invasion depth of the new drilling fluid on FA sand bed is only 4.0 cm,and on HTHP sand bed this invasion depth is 5.2 cm.The low surface tension of the mud filtrates is 22.1 mN/m,which is efficient in minimizing the damage caused by water block.Recovery of permeability is greater than 90%,an indication of good reservoir protection.Application of this drilling fluid technology on 4 wells reveals that the drilling fluid has stable performance,its properties easy to maintain,and average drilling time reduced by 11.73 days.Wells drilled with this drilling fluid do not necessitate acidization and fracturing,and flow at first production.The average flowing production rate has been 7.88 t/d.This drilling fluid has been successfully used in the Block 43,and the practices are of importance for the development of old oilfields in Shengli area.
Reaction of Mud Cake Solidifying Agent with Cement Slurry Filtrate in the Annulus Between Cement Sheath and Formation
CUI Yunhai
2016, 33(2): 69-74. doi: 10.3969/j.issn.1001-5620.2016.02.015
The quality of cementation between cement sheath and borehole wall plays an important role in efficient producing a well.A study on the reaction mechanism of mud cake solidifying agent and filtrate of cement slurry has been conducted based on mud cake solidification technology and modern analysis and test technology.It reveals that the effective constituents of the solidifying agent under pressure will diffuse toward the mud cake,adsorb on the mud cake and finally go into the mud cake.Reaction of the solidifying agent and cement filtrate produces gelled substances such as hydrated calcium silicate (C-S-H) and hydrated calcium aluminate (C3AH6) of low polymerization degrees.These gelled substances,with time,will turn into high polymerization degree hydrated silicates,a process in which in the first 3 days,the quantity of monomer silicates decreases rapidly,the quantity of dimer silicates,at the same time,increases at first,and then decreases.These monomers and dimers will finally become silicates of high polymerization degree,making the mud cake solidified,hence improving the cementation quality of cement sheath and borehole wall.
A Model Predicting Elastic Moduli of Multi-component Set Cement
LIU Jian, ZHANG Linhai, TAO Qian, LIU Wei, ZHOU Shiming, WANG Lishuang
2016, 33(2): 75-78. doi: 10.3969/j.issn.1001-5620.2016.02.016
Complexity and poor repeatability of the procedure for the testing of the elastic moduli of multi-component set cement,and the lack of theoretical model in predicting the elastic moduli have led to the use of high precision compressive bending test machine to study the changing pattern of,and to build a prediction model for the elastic moduli of multi-component set cement.It has been found that for two-component set cements,their moduli at elastic components concentration of 0 and 0.2(volume fraction) can be used to predict the change of modulus with the composition of the cement,because a linear relationship exists between the composition and the modulus.For multi-component cement,this linearity does not exist between the elastic components concentration of 0 and 0.2(volume fraction).In this case,inverse method and correlation-coefficient method are to be used to predict the elastic moduli of the set multicomponent set cement.This model is of importance in minimizing the experimental workload and in theoretical study of the elastic moduli of the multi-component set cement.
High Temperature Salt Resistant Nonionic Anti-channeling Styrene Butadiene Latex
QI Ben, FU Jiawen, SUN Qinliang, LIU Wenming, YU Qianqian, DU Bin
2016, 33(2): 79-83. doi: 10.3969/j.issn.1001-5620.2016.02.017
Oil well cement slurries treated with nonionic styrene-butadiene latex have poor stability,low temperature tolerance and low salt resistance,not suitable for cementing high temperature deep wells or wells with complex borehole profile.An anti-channeling latex,BZT-L2,has recently been developed by adding two alkylphenol ethoxylate of different degrees of polymerization into the nonionic styrene-butadiene latex.Evaluation of the BZT-L2 latex revealed that a cement slurry treated with 8% of the latex at temperatures between 30℃ and 170℃ had API filter loss controlled less than 50 mL,and the latex can be used in saturated salt system.The latex treated cement slurries had good stability and the thickening curves were right-angled.BZT-L2 not only reduced filter loss of the cement slurries,it also rendered the cement slurries anti-channeling capability.The non-ionic styrene-butadiene latex had good compatibility with other cement slurry additives,and the general properties of cement slurries,such as rheology,free water and stability have all been excellent.
Solutions to Difficulties Met in Gas Well Cementing in Block Anaco (Venezuela)
ZHANG Weibin, MA Zhihe, LI Jianhua, LIU Yong, ZHANG Chunmei, HUO Mingjiang
2016, 33(2): 84-87. doi: 10.3969/j.issn.1001-5620.2016.02.018
Drilling in the Block Anaco,Venezuela has encountered downhole problems such as low formation fracturing pressure gradient,high pressurized formation water and low pressure gas zones,as well as gas channeling in annulus,often accompanied by H2S and CO2.Lithology of formations where these problems have been met is argillaceous sandstone.It has been ascertained that troubles met in the cementing operations in this block come from cement and the variety of formation conditions.Solutions to these problems lie in the correct understanding of the effects of geological conditions on well cementing and selection of proper cementing materials and technology.Studies on stage cementing,dual-density or multi-density cement slurries and the selection cementing additives have been conducted.Experiments on corrosion depth and gas channeling prevention have been done.The studies and experiments reveal that the minimum density for anti-channeling anti-corrosion cement slurry is 1.2 g/cm3,and the density difference between the top and bottom of the cement column shall not be greater than 0.03 g/cm3.Free water should be near 0,and the set cement should have high compressive strength and low permeability.Use of corrosion inhibitor BCE-750S in cement slurry of common silicate cement greatly reduced the 7 d,30 d and 60 d corrosion depths in the set cement,solving the gas channeling in annulus and H2S/CO2 problems in the Block Anaco.
Anti-channeling HTHP Liner Cementing Technologies Used in Block Shunnan
LU Feifei, WANG Yonghong, LIU Yun, LI Fei, BAN Shengfu, ZHU Wenhao
2016, 33(2): 88-91,95. doi: 10.3969/j.issn.1001-5620.2016.02.019
Ultra-high formation temperatures,complex formation pressure system,active formation gases have long resulted in difficulties in well cementing,such as gas channeling and poor cementing job quality.Studies on HTHP anti-channeling cementing optimization reveal that 0.18 mm,0.125 mm and 0.09 mm silica sand can be used in cementing slurries to solve the decreasing of HTHP strengths of set cement at 178℃.Latex cement slurry,when treated with active SiO2 water suspension,has enhanced gas channeling control performance.Addition of fibers in latex cement slurry reduces the elastic modulus of the set cement by 48%,greatly improving the impact resistance of the set cement.Right-angle thickening set cement has better gas channeling control.To prevent the column of the cement slurry from losing weight,therefore destabilizing the gas zones to be cemented,reverse circulation after mud displacement should be carried out and pressurize the annulus as soon as possible,a way to effectively control gas channeling.High temperature gastight cementing tools and accessories will also help control gas channeling.Using technologies,gas-channeling control in cementing of the φ177.8 mm liner string has been successfully realized in the Block Shunnan.These technologies are of importance to gaschanneling control in HTHP well cementing in the block.
A Visual Test Apparatus for Flushing Fluid Evaluation and the Evaluation Method
LI Shaoli, ZHOU Zhanyun, YAO Zhixiang, LI Zhimin
2016, 33(2): 92-95. doi: 10.3969/j.issn.1001-5620.2016.02.020
In flushing fluid evaluation,no standardized methods are available;some evaluation apparatus developed in recent years are not able to simulate the real situation of field operation,and quantitatively evaluate the performance of flushing fluid.A new visual test apparatus for flushing fluid evaluation has recently been developed,which consists of fluid storage tank,circulation pump,flow rate controller,flow meter,simulated wellbore,backflow conduit,heating device,liquid drain,and roller.This apparatus is able to simulate the formulation of flushing fluid,flushing time and flow rate etc.,and the flushing performance can be visually checked because a transparent glass pipe is used as the simulated borehole.The flushing time can be determined by visualization and the critical flow rate can be determined for optimum flushing.As a quantitative,visual evaluation apparatus,it is able to satisfy the needs for field application.
Comparison and Analysis of Thickening Experiment Methods for Chemically Foamed Cement Slurry
YANG Xianyu, YUE Ye, CAI Jihua
2016, 33(2): 96-100. doi: 10.3969/j.issn.1001-5620.2016.02.021
Consistency tester is used to measure the thickening of cement slurry.For foamed cement slurries,air contained in the slurries often results in errors in consistencies measured.To minimize the effects of air on the consistency of cement slurry,three methods have been used to measure the consistencies of foamed cement slurries treated with different concentrations of foamers,and an optimized measuring method has been selected.Sources of the errors have been analyzed,and the consistency curves obtained from the optimized measuring method corrected through mechanical analyses and calculation.It was found that the residue foamers in cement slurry accelerated the thickening process,and the thickening time of the cement slurry containing residue foamer was 41% less than that of the cement slurry with no residue foamer,indicating that the effects of residue foamer should not be ignored.In two consistency tests with one cement slurry containing air and another one containing no air in it,the differences in thickening times were small (1 min and 11 min,respectively),while the shapes of the thickening curves were quite different;the thickening curve of the foamed cement slurry was more of right-angled.Cement slurry containing less air,or cement slurry with later consistency increasing faster,difference between the thickening times before and after correction was small;for chemically foamed cement slurries,this time difference was only 3 min when the consistencies before and after correction had both reached 100 Bc.For cement slurries with low density and high air content,or cement slurry with its later consistency increasing slowly,the consistency measured has to be corrected.
Rheology of Thickened 100% Liquid CO2 Fracturing Fluid
CUI Weixiang, QIU Xiaohui
2016, 33(2): 101-105. doi: 10.3969/j.issn.1001-5620.2016.02.022

A surfactant thickening agent suitable for use in dry-fracturing with liquid CO2 has been developed.The thickening process of liquid CO2 was simulated online through high pressure pipe flow rheological experiments.Results of the experiments have revealed that the surfactant forms rods or wormlike micelle in liquid CO2,thereby increases the viscosity of the liquid CO2 by 86-218 times of the original viscosity.The liquid CO2 treated with the thickening agent has shear-thinning characteristics.Increase in pressure or increase in the volumetric fraction of the thickening agent has smaller effect on the viscosity and rheology of the thickened liquid CO2 fracturing fluid,and the effective viscosity of the fracturing fluid decreases exponentially with increase in temperature.The thickened liquid CO2 fracturing fluid has flow index that increases with increase in temperature,and consistency factor that decreases with increase in temperature.

Effect of Nano ZnO on Rheology of CTAC Wormlike Micelle
JIA Shuai, QIN Wenlong, YANG Jiang, LIU Xuan, ZHOU Yining
2016, 33(2): 106-110,116. doi: 10.3969/j.issn.1001-5620.2016.02.023

The unique surface natures of nano materials make them suitable for modification to produce oilfield chemicals of excellent performance.The optimum ratio is studied that cetyltrimethyl ammonium chloride (CTAC),a clean fracturing fluid additives commonly used in China,to form worm-like micelle with sodium salicylate (NaSal).Nano ZnO was used to modify the property of the worm-like micelle solution through quasi-crosslinking,and the mechanism of nano ZnO in enhancing the viscosity,thermal stability and shearing stability was analyzed.The mass fraction of ZnO needed for the modification was optimized.In laboratory experiments,the viscosity of the micelle solution reached the maximum value at CTAC:NaSal=1.25:1(molar ratio),and so does the length of the micelle.The micelle solution has the best viscosifying performance at 0.2% of ZnO,and the viscosity of the solution is maintained at 60 mPa·s at 90℃,even after long time of shearing and heating.CTAC micelle solution modified with nano ZnO shows elasticity as a whole,and its rheological behavior conforms to Maxwell rheological model,as demonstrated by Cole-Cole fitting.This micellesolution is a linear viscoelastic fluid with single relaxation time.

Study and Application of Stimulation Fluid for Shale Reservoirs
LU Li, CHEN Ying, XU Tingting, ZHANG Xiaohu
2016, 33(2): 111-116. doi: 10.3969/j.issn.1001-5620.2016.02.024

Reservoir shalesare generally brittle and full of naturalfractures and beddings.They have low porosity and extremely low matrix permeability.Fracturing of shale reservoirs in the Sichuan Basin has been done mainly with slick water or "slick water plus linear gel" at high volume and high flow rate.Based on the nature of the shale reservoirs,an SD conventional slick water fracturing fluid and an SD linear gel for shale gas operation have been developed.The SD slick water fracturing fluid and the SD linear gel are of low friction,low damage to reservoir permeability and high inhibitive capacity.In field applications,the SD slick water fracturing fluid and the SD linear gel demonstrated good salt resistance,stable properties,and reduced flow friction.Both were very easy to prepare and the use of water was highly efficient because the fracturing fluid can be recovered for reuse.With the application of the SD slick water fracturing fluid,high salinity flowback fracturing fluids can be recovered for reuse,satisfying the needs for economic and environmentally friendly development of shale gas.

Preparation and Application of Modified Biopolymer Fracturing Fluid
MING Hua, ZHAI Wen, FAN Yongjie, JIANG Zhiqiang, LIU Wei
2016, 33(2): 117-121. doi: 10.3969/j.issn.1001-5620.2016.02.025

FAD-120,a modified (through etherification) biopolymer is made to overcome conventional biopolymer's deficiency,such as high consumption and low temperature stability.FAD-120 is suitable for use in fracturing tight reservoirs,whose formation temperature is in the range of 70-130℃.FAD-120 is ready to dissolve in water,even in high salinity saltwater.FAD-120 solution has low friction coefficient,good sand-carrying capacity and low residue (hence low formation damage),and is environmentally friendly.Fracturing with FAD-120 is much easier to operate than guar gum.FAD-120 is also cheaper than guar gum,and can be used in water of different quality.In a field application in Block Chi-228 in Changqing,shallow underground water having salinity of 3,334 mg/L was used to prepare the fracturing fluid;the maximum sand content was as high as 25%.In the same block,sand consumption in fracturing a single well is almost the same as guar gum fracturing fluid.The success of FAD-120 is of great significance in fracturing fluid preparation with water of different quality,reducing the cost of fracturing fluid,and in ensuring the operation of large-scale volumetric stimulation of reservoir.

Weighted Clean Fracturing Fluid for Deep Well Stimulation
LIU Tongyi, CHEN Jiangming, ZHAO Zhongcong, YU Yi, LIN Bo
2016, 33(2): 122-126. doi: 10.3969/j.issn.1001-5620.2016.02.026

High temperature borate cross-linked guar gum fracturing fluids have long been used in fracturing deep,low permeability and high temperature reservoirs.High friction and the difficult-to remove residues of the fracturing fluids are two problems that have to be faced with in the fracturing jobs.A thickening agent,with acryl amide and ionic functioning groups as the molecular backbone,is developed for use in fracturing fluid.It has a certain degree of hydrolysis.A weighted clean fracturing fluid,BCG-1,has been formulated using this thickening agent and other additives carefully selected.In laboratory experiments,BCG-1 demonstrated good high temperature and shear resistance performance.The viscosity of BCG-1 maintained at 57 mPa·s or higherafter shearing 120 min at 160℃ and 170 s-1,and good repeatability of the experiments can be obtained.Friction test on 8 mm flow tubes reveals that ZJFA-1,an extender for the fracturing fluid,greatly reduces the friction of BCG-1.NaNO3 as a weighting agent has almost no effect on the friction of BCG-1.BCG-1,after gel-breaking,has a viscosity less than 21 mPa·s,and residue content less than 5 mg/L,characteristic of clean fracturing fluid.