2015 Vol. 32, No. 5

Display Method:
2015, 32(5)
2015, 32(5)
High Performance Water Base Drilling Fluid for Shale Gas Drilling
YAN Lili, LI Congjun, ZHANG Zhilei, SUN Jinsheng, XU Xianguang, SU Yinao
2015, 32(5): 1-6. doi: 10.3969/j.issn.1001-5620.2015.05.001
High performance drilling fluids used in conventional drilling are not able to satisfy the needs for long horizontal section shale gas drilling, and the use of oil base drilling fluids, on the other have, always means high cost and pollution to environment. A high performance shale inhibitor (dark brown liquid), a particles of nano/micro meter in diameter, a filming filter loss reducer, and a lubricant have been developed to formulate a high performance water base drilling fluid. The evaluation of this fluid has rheology, filtration control, lubricity and inhibitive capacity that are comparable to those of oil base drilling fluid, meaning that this drilling fluid is suitable for shale gas drilling. A drilling fluid of 2.05 g/cm3 has its friction coefficient reduced by 26% after treatment with the lubricant. This drilling fluid can form a thin layer of film around the surface in contact with it, thereby sealing off the micro-fractures and cutting of the channels through which pressure are transmitting. Shale cores rinsed for 10 h in this drilling fluid still retains high strength, meaning that this fluid has good inhibitive capacity. This drilling fluid has been used in the drilling of the Well YS108H4-2 in Huangjinping, Zhaotong, and the drilling operation encountered no downhole troubles and difficulties, and the wireline logging is successful. No hole enlargement was found, and the ROP was 11.74 m/h.
Performance Evaluation of Powdered Oil Base Mud Emulsifier
LIU Minghua, ZHANG Bin, WANG Yang, HUANG Guichun, SUN Ju, WANG Zhonghua
2015, 32(5): 7-9. doi: 10.3969/j.issn.1001-5620.2015.05.002
A powdered emulsifier used in oil base drilling fluid is synthesized using 2, 6-diaminopyridine, amine and organic acids. It has melting point of 120℃ and HLB value of 1.7. As a vitrescentmaterial this emulsifier is easy to pulverize. Characterization of this emulsifier shows that amidation has taken place in the synthesis process, proved by the presence of -CONH2 peak in the IR spectrum. At a treatment of 3% in oil base drilling fluids with different oil/water ratios, good emulsion stability is obtained. Oil water emulsion with oil/water ratio of 7:3 has emulsion stability (ES) voltage of 600 V and 100% emulsification. Oil base muds treated with this emulsifier have ES voltage of 625 V, temperature stability of 180℃ and YP/PV ratio of 0.30 Pa/mPa·s. Newly prepared oil base muds treated with this emulsifier has stable properties after aging at 150℃ for 48 hours, and the ES voltage is greater than 700 V, indicating that this emulsifier has good emulsifying capacity and high temperature stability.
Study on Lost Circulation Prevention While Drilling Using Oil Base Drilling Fluid
LIU Junyi, QIU Zhengsong, LUO Yang, WANG Weizhong, WANG Qiang, HUANG Daquan, ZHANG Xianbin
2015, 32(5): 10-14. doi: 10.3969/j.issn.1001-5620.2015.05.003
Different lost circulation materials have been selected and tried to prevent loss of oil base mud which always resulted in much higher drilling cost compared with water base drilling fluid. A new lost circulation material (LCM) was developed for use in oil base drilling fluids. This LCM is a lost circulation prevention while drilling agent, and is compatible with many other LCMs. In laboratory studies, rigid bridging particles, elastic packing particles and fine particles of fibers work synergistically, and can swiftly form dense plugging and sealing layers to prevent lost circulation of oil base drilling fluids. An oil base drilling fluid formulated with this LCM is tested for its properties before and after hot rolling (at 120℃ for 16 h). This fluid has filtration rate through PPA sand bed of only 11.4 mL, and it also has satisfactory rheological properties.
Development and Evaluation of Oil Base Mud Plugging Agent with Nuclei
KUANG Xubing
2015, 32(5): 15-18. doi: 10.3969/j.issn.1001-5620.2015.05.004
An acrylic resin polymer was synthesized with monomers such as butyl acrylate, octadecyl acrylate, acrylic acid and styrene through modified emulsion polymerization. A modified organophilic silica flour was used as condensation nucleus. This synthesized polymer is a polymer with nuclei, and is used as a plugging and sealing agent in oil base drilling fluids to prevent mud losses and borehole wall collapse. It is of almost no influence on the rheology of oil base muds, and can greatly improve the capacity of oil base muds to build high quality mud cakes and the emulsion stability of oil base muds. Cores flooded with oil base mud formulated with this polymer have pore throats plugged by more than 75%, and breakthrough pressure can be as high as 10 MPa or higher. This plugging and sealing agent has excellent high temperature stability, the plugging performance remains almost unchanged before and after aging. As laboratory experiments indicated, this plugging and sealing agent is better than asphalt products.
Effect of Gas Composition on the Formation of Gas Hydrates in Drilling Fluid
GAO Shuyang, WANG Chengbiao, SHI Bingzhong, HE Yong, LIU Rui, TANG Cuiping
2015, 32(5): 19-22,26. doi: 10.3969/j.issn.1001-5620.2015.05.005
Gas hydrates are easy to form in deep-water drilling, imposing great dangers to the drilling operation. Conditions under which gas hydrates are formed vary with gas composition, making it difficult to prevent the formation of gas hydrates. Using a newly developed device, the kinetics of the formation of natural gas hydrates in two water base drilling fluids is studied. Of the three gas compositions, the "Green canyon gas" forms gas hydrates in drilling fluid most easily, methane is the most difficult forming gas hydrates, with the simple gas mixture in between. With other conditions being the same, it is much easier for alkane of higher molecular weight to form gas hydrate in drilling fluids.
Protective Test Fluid for Deepwater Reservoir:Study and Application in Block Lingshui17-2
MENG Wenbo, LI Weiping, ZHANG Chong, YAN Bangchuan, XU Fei, XIANG Xingjin, BAO Rong
2015, 32(5): 23-26. doi: 10.3969/j.issn.1001-5620.2015.05.006
Individule water molecules can form complexed water through intramolecular and intermolecular networking by hydrogen bonds between HWLH, a complex agent, and water molecules. HWLH has the ability to stop water from migration between test fluid (containing HWLH) and formation, protecting reservoirs from being damaged. Laboratory studies show that HWLH test fluid has good rheology, inhibitive capacity, water block prevention capacity (air-liquid interfacial tensions are 25.7-25.9 mN/m), low corrosion and good gas-hydrate inhibition. HWLH test fluid is compatible with early stage work fluids, test fluids for non-reservoir sections and formation water. HWLH test fluid has been successfully used in testing of the gas well Lingshui 17-2-1.
High Temperature High Density Drilling Fluid Technology for Yinggehai Basin
ZHANG Qun, LIU Jianquan, JIANG Guancheng, WANG Dongchao
2015, 32(5): 27-31. doi: 10.3969/j.issn.1001-5620.2015.05.007
Reservoir formations in Yinggehai Basin are of high temperature (186-218℃) and high pressure (coefficient of formation pressure:1.6-2.4). Failure to maintain stable properties of the drilling fluids currently used at high temperature leads to high viscosity which in turn makes weighting of the drilling fluids very difficult. Poor performance of the drilling fluids also caused damage to reservoirs. Optimization has been done to the drilling fluids recently based on the understanding of the formation geology and analysis of the mechanism of formation damage. Ultra-fine calcium carbonate powder and a broad spectrum oil-film temporary sealing agent were added to form high-quality mud cake and tough thin-film. Surfactants were used to improve the surface properties of formation rocks, in an effort to prevent water block from happening. White oil, together with the surfactants, contributes to the temperature stability of the drilling fluids. The optimized formulation remains stable at 200℃ and 2.2 g/cm3, satisfying the needs for drilling operation. Cores flooded with this drilling fluid have permeability return of 90%. It is also resistant to CO2 contamination.
Mechanism of Synergistic Inhibition of Water Base Drilling Fluids on South Edge of the Dzungaria Basin
YANG Y, ong, XIE Lianyun, SUN Xiaorui, RONG Kesheng, PU Xiaolin
2015, 32(5): 32-36. doi: 10.3969/j.issn.1001-5620.2015.05.008
Drilling fluids containing inorganic and organic compounds are used in the south edge of the Dzungaria Basin, to drill formation rocks that are sensitive to water invasion and are easy to hydrate, swell, disperse and slough. Different kinds of shale inhibitors were tested in laboratory for their ability in inhibiting shale dispersion and swelling, both used as a single additive and used in combination. The testing results are used to formulate an inhibitive drilling fluid, and its performances were again tested. In these tests, the c-spacing, zeta potential, distribution of particle sizes, water activity and adsorptive capacity of clays were measured in an effort to reveal the working mechanism of shale inhibitors used in water base drilling fluids in the south edge of the Dzungaria Basin. It shows that KCl functions remarkably in crystal lattice fixation, electric double layer compression and enhancement of polymer adsorption. Compound organic salts, to some extent, can fix crystal lattice, remarkably compress the thickness of electric double layer, and adjust the water activity. Modified poly glycol has the ability of adsorption on to the surface of clay particles and therefore encapsulation of the clay particles. Poly glycol also synergistically functions with KCl. A combination of multiple shale inhibitors in water base drilling fluids therefore has these functions such as crystal lattice fixation, electric double layer compression, water activity adjustment, adsorption on the surface of clay particle and encapsulation, which are working synergistically.
Laboratory Study on Environmentally Friendly Polymer Shale Inhibitor
QIN Yong, HUANG Ping, WAN Wei
2015, 32(5): 37-40. doi: 10.3969/j.issn.1001-5620.2015.05.009
KCl polymer drilling fluids are currently commonly used in Sichuan and Chongqing areas. The KCl polymer drilling fluids used contain high concentration of chlorines which, when reacted with organic compounds in the surrounding environment, will generate chlorinated chemicals having teratogenesis, carcinogenesis and mutagenesis effects. A polyethylenepolyamine, havingdegree of amination of more than 85%, was synthesized through Hofmann Reaction from polyacrylamide. It has LC50(opossum shrimp) of 18,764 mg/L, actually non-toxic, and BOD5/CODCr of 68.2%, easy to degrade. In laboratory evaluation, the polyethylenepolyaminesolution reduced the linear rate of swelling of cores by 56.79%, and increased the rate of recovery of shale cuttings by 61.84%, while KCl solution reduced the linear rate of swelling of cores by 22.75%, and increased the rate of recovery of shale cuttings by 43.03%.This polyethylenepolyamine is also superior to KCl in reducing the capillary suction time (61.84% against 34.62%). These results show that the polyethylenepolyamine is a better shale inhibitor than KCl.
Borehole Instability and Countermeasures Taken in Drilling Deep Complex Rock Formations in Nanpu
ZHAO Yaning, CHEN Jinxia, LU Shuqin, ZHU Kuanliang, XING Daokuan, JIN Zhitie
2015, 32(5): 41-45. doi: 10.3969/j.issn.1001-5620.2015.05.010
Borehole instability has been taking place in drilling the Dong-Er member of the No. 3 Structure in Nanpu. It is found that micro-fractures are quite developed in the deep shale formations, which, under differential pressures, causes water imbibition into the fractures. The absorbed water increases pore pressure of the formations and causes formation to hydrate. Un-uniformity of forces developed in the formations as a result of hydration further enlarges the opening of fractures. Edgetone effect of pressures exerted by drilling fluid causes formation rocks near the borehole wall to slough. Laboratory experiments show that the key to the success of borehole stabilization is to plug and sealthe fractures. A KCl drilling fluid is formulated with 3% FT3000, a plugging agentwithhigh softening point, SPNH, SMP, and 0.8% DSP, a filter loss reducer having viscosifying effect. This drilling fluid has superior plugging and sealing performance as shown in laboratory experiments. In field applications, borehole collapse has been remarkably minimized, and drilling time is reduced from 119.25 d in 2012 to the present 46.4 d, and ROP increased from 6.65 m/s to 12.05 m/s.
Development of New Gel-breaking Flocculant for Waste Water Base Drilling Fluid Treatment
LI Guanghuan, WU Wenru, HUANG Daquan, MA Hong, GU Yanfeng, CHEN Jianxin, LONG Tao, LI Yecheng
2015, 32(5): 46-48,53. doi: 10.3969/j.issn.1001-5620.2015.05.011
A new gel breaker, BZ-CAF, made from three monomers, acrylamide (AM), methacryloxyethyltrimethyl ammonium chloride (DMC) and acryloyloxyethyltrimethyl ammonium chloride (DAC), is developed for use as gel-breaking flocculent in waste water base drilling fluids. This high molecular weight polymer has no metal ions in its molecules, and can break the gel structures developed in a drilling fluid, while minimizes its effect on the properties of the new drilling fluid formulated from the old fluid. An ultra-high molecular weight ionic polymer secondaryflocculant, BZ-AAF, is synthesized with acrylamide and AMPS. Waste drilling fluids treated with BZ-CAF and BZ-AAF have COD removed by 94.03%, chroma elimination by 93.83%, and oil removed by 85.86%. Liquid separated from the treated waste drilling fluid can be used to formulate new drilling fluid with stable properties that are comparable to those formulated with fresh water. BZ-CAF and BZ-AAF have been used in 5 wells in Dagang oilfield, showing their potential in environment protection and water source economization.
Analysis of Abnormal Thickening Behavior of the Class G High Sulfate Resistance Oil Well Cement
GU Guangwei, YAO Xiao, ZHOU Xingchun, XIAO Li, WANG Ping, WANG Daquan
2015, 32(5): 49-53. doi: 10.3969/j.issn.1001-5620.2015.05.012
Some cement slurries formulated with class G cement are studied for the improvement of their poor thickening performance. Clinkers made from raw materials containing high concentration of MgO and unstable components have higher MgO and C3A (4.51% and 7.21%, respectively), and the produced cements in turn have high alkaline and f-CaO concentration (1.97%) and low SO3 concentration (0.42%). Calcination at low temperatures, denser packing of raw material in kiln with limited space, and inadequate cooling all lead to unduly short thickening time. Higher concentrations of C3A and C4AF in clinkers will result in poor compatibility of cement slurry with additives and abnormal thickening behavior of that cement slurry.
Cementing of Wells with Lost Circulation in Rumaila Oilfield
LI Xiaoqi
2015, 32(5): 54-57. doi: 10.3969/j.issn.1001-5620.2015.05.013
Low fracturing pressures of the Damman and Hartha formations in the Rumaila Oilfield have been causingmud losses in cementing the technical casing strings. The existence of borehole wall washout (erosion) and tight holes have resulted in poor cement slurry displacement. To overcome these problems, a plug flow low friction prepad fluid has recently been developed. This prepad fluid, having densities between 1.00 g/cm3 and 1.80 g/cm3, was formulated with non-polymeric suspending agent DF-1, flushing agent DF-3, and organic solvent, DF-4, as flow pattern modifier. It has low flow friction, high flushing performance and easy-to-control rheology, which help improve the displacement efficiency of cement slurry at low flow rates. A low density (1.00-1.35 g/cm3) cement slurry was formulated with nano silicon sol as the stabilizer to improve the settling stability of the slurry. The compressive strength of the set cement at room temperature after 48 h is greater than 14 MPa. Cementing techniques using the prepad fluid and the cement slurry were developed as guidance for proper field operation. The prepad fluid and the cement slurry have been successfully used on 5 wells, with no lost circulation. Number of well sections cemented with acceptable job quality is increased by 21%.
Study and Application of Anti-channeling Cement Slurry Used in Shallow Gas Zones in Bohai
LI Houming, XIANG Xianzhong, ZHANG Hao, FU Junfang, ZHAO Hu
2015, 32(5): 58-60. doi: 10.3969/j.issn.1001-5620.2015.05.014
Two optimized cement slurries are designed to deal with sustained casing pressure problem in cementing shallow gas zones in Bohai, with the first one prepared with expanding material and plasticization agent, the second one with self-healing material. When expanding material and fibers are added into a cement slurry, the 96-hour cement strength of the slurry is increased only by 15%, which means that the anti-channeling capacity of the cement slurry will not be improved notably. When seal-healing material is added into the cement slurry, the sealing efficiency of the set cement reaches 95%, or even higher. It is thus believed that cement slurries treated with self-healing material satisfy the need for well cementing, and this is also proved by field practices.
Study on Self-healing Mechanism of Self-healing Prepad Fluid for Well Cementing
YANG Zhenjie, FENG Jingjing, LIAO Tao, MA Chengyun, WU Xingxing
2015, 32(5): 61-65. doi: 10.3969/j.issn.1001-5620.2015.05.015
Cylindrical sliced set cement slurry sample (water cement ratio of 0.44) aged in steel pipe were placed in clear water and self-healing prepad fluid for ageing. Using X-ray instrument, the aged slice samples were tested for their anti-channeling capacity and analyzed for their micro structures and composition of hydration product. The Ca(OH)2 content of the samples were measured with TG/TGA method. Using mercury porosimeter, the pore structure of the samples were analyzed. ESEM was finally used to survey the microscopic topography. It was concluded that the prepad fluid can infiltrate into the micro-fractures of the samples, where the prepad fluid reacted with the Ca(OH)2 and nonhydrated cement existed there to form hydrated product, thus realizing self-healing. The prepad fluid also infiltrate into the pores of the main body of the samples to activate hydration reaction, producing hydrated calcium silicate gel which can fill the pores in the main body, thus strengthening the main body and enhancing its ability to counter filtration and damage. The study is of importance in the application of self-healing prepad fluid, and for the success of well cementing.
Mechanism of Calcium Carbonate Whisker Enhancing Cement's Resistance to Contraction and Its Application
GUO Xiaoyang, TANG Qi, HUANG Chengxia, LIN Luan
2015, 32(5): 66-68. doi: 10.3969/j.issn.1001-5620.2015.05.016
Perforation, acidizing and fracturing operations often cause damage to the integrity of cement sheath. Volumetric contraction of cement during hydration process always produces micro fissures and micro annulus, forming channeling path for channeling between formations, which in some cases may cause oil and gas to channel to the surface. These problems are brought about by the lack of toughness of set cement and the volumetric contraction of cement slurry during hydration. In laboratory studies, calcium carbonate whisker was added to cement slurry at 0, 1%, 2%, 3% and 4%, respectively, and the flexural strengths, compressive strengths, rate of volumetric contraction, and the overall properties of the set cement at 1, 3, 7, 14 and 28 days, respectively, were measured. Compared with cement slurry without treatment of calcium carbonate whisker, cement slurries treated with 3% calcium carbonate whisker, after aging for 28 days, had compressive strength increased by 36%, flexural strength increased by 33.67%, and volumetric contraction reduced by 82.97%. The overall properties of the cement slurry also satisfied the need for well cementing.
Effect of Gas Volume Fraction in Foam on Performance of Foam Cement Slurry
XIAO Jingnan, FANG Chunfei, ZHOU Shiming, ZHANG Mingchang, Ding Shidong, SANG Laiyu, ZHAO Shanshan
2015, 32(5): 69-72. doi: 10.3969/j.issn.1001-5620.2015.05.017
The properties of foam cement are mainly determined by the gas volume fraction of foam. A foam cement slurry with good settling stability was formulated by adding 3%-5% of foaming agent and 0.05%-0.10% of foam stabilizer. The effect of gas volume fraction of foam on the performance of foam cement was studied. An increase in the gas volume fraction of foam increases the viscosity and reduces the filtration rate of the foam cement slurry. The increase in the gas volume fraction also leads to the following results:a linear decrease in the compressive strength of set cement, an increase in gas permeability, and an enhancement of elastoplasticity. Higher compressive strength and better elastoplasticity of set cement can be obtained when the gas volume fraction is controlled around 30%, and the requirements of cementing gas zones can be satisfied.
Development and Evaluation of Supramolecular Fracturing Fluid
JIANG Qihui, JIANG Guancheng, LIU Chong, WANG Chunlei, ZHU Qi
2015, 32(5): 73-77. doi: 10.3969/j.issn.1001-5620.2015.05.018
Crosslinking polymer fracturing fluids presently used have poor shear-thinning performance, therefore relying on high viscosity forsand carrying. Moreover, these fracturing fluids, because of their high residue contents, have been causing reservoir damage. A supramolecular polymer has recently been developed and a fracturing fluid of simple formulation has been prepared. Laboratory studies show that this fracturing fluid has viscosity of 140 mPa·s after shearing at 130℃ and 170 s-1 for 2 h. Settling velocities of a proppant in this fracturing fluid at 24 h and 48 h are 3.7×10-4 mm/s and 5.6×10-4 mm/s, respectively. At 80℃, this fracturing fluid, 2 h after treatment with potassium persulfate at a concentration of 0.05%, has a viscosity of 1.32 mPa·s and a surface tension of 25.23 mN/m. The fracturing fluid, with gel broken, is transparent, and has almost no residues. It has an initial filtration volume of 2.32×10-3 m3/m2, a filtration coefficient of 1.86×10-4 m3/min0.5, and a filtration rate of 3.23×10-5 m/min. Damage of the filtrate of the fracturing fluid to the matrix of cores is 10.8%. These properties make this fracturing fluid suitable for use in the fracturing of tight gas reservoirs.
Study on and Application of a Polymeric Thickening Agent for Fracturing Fluid
LI Zhizhen, YANG Xu, TU Yinghong, HUANG Jing, MI Hongfu
2015, 32(5): 78-82. doi: 10.3969/j.issn.1001-5620.2015.05.019
A cationic polymeric thickening agent used in fracturing fluid was developed for use in formations of middle or high temperature. Analyses of the thickening agent using IR spectrum, NMR and SEM showed that a spatial network was formed by the molecules of the polymer after reacting with an electric-attraction inducer, rendering the polymer very good thickening capacity. This polymer has viscosity between 40-55 mPa·s after shearing at 170 s-1 at 110℃ and 130℃ for 1 hour. Time for gel breaking was 71.5 minutes at 90℃. No residue was left after gel breaking, meaning that reservoir damage caused by this polymer would be very low (12.7% in an experiment.) Fracturing fluid formulated with this polymer showed very good viscoelasticity, and sand carrying capacity, rate of sand sedimentation being 1.96×10-4 m/min. At normal temperature, fracturing fluid containing 60% sands still showed good suspension stability after standing for 1 hour. As a cost-effective material, it satisfied the need for field fracturing operation, as shown in the fracturing of the lower segment of HE-8 in Well Su20-23-X, Sulige gas field.
Selection of Tracers Used in Guar Gum Fracturing Fluid
CHI Xiaoming, LI Xuhang, ZHANG Shihu, MA Xiaopeng
2015, 32(5): 83-85. doi: 10.3969/j.issn.1001-5620.2015.05.020
In oil and gas development, most often the reservoirs are fractured in staged fracturing manner, and all the fracturing fluids entering into each zone are flowed back together to the surface. This process can be used to assess the backflow of the fracturing fluid as a whole, and is incapable of assessing the backflow of fracturing fluid form each single zone. To assess the backflow of the fracturing fluid from each single zone, tracers are added to the fracturing fluid into each zone at certain concentrations. Then the backflow is sampled continuously to detect the concentration of tracers therein, and the efficiency of the backflow of each zone can thus be determined. Tracers used in this process should be compatible with the fracturing fluid. In a series of laboratory experiments, low molecular weight alcohols and inorganic ions is proved not suitable for use as tracers in guar gum fracturing fluids, two other substances, TA and TB, on the contrary, are compatible with the guar gum, and have low adsorption in most reservoir environments (indicating that their use will notaffect the concentration measurement at the surface.), and are suitable for use as tracers in guar gum fracturing fluid.
Study and Application of High Temperature Low Concentration Guar Gum Fracturing Fluid
LUO P, eng, ZHANG Junjiang, YAN Yujie, ZHANG Xiong
2015, 32(5): 86-88. doi: 10.3969/j.issn.1001-5620.2015.05.021
Fracturing fluids containing 0.45%-0.50% guar gum had always been used in the stimulation of high temperature, low porosity, low permeability reservoirs. High concentration of guar gum resulted in serious damages to reservoirs and high operation cost. Laboratory studies had been conducted to try to minimize the use of guar gum and to enhance the thermal stability of fracturing fluids. A high performance guar gum and a cleanup additive of low surface tension were selected for use with the newly developed multi-group crosslinker with bigger hydrolysis radius. Using these additives, a fracturing fluid with high thermal stability and low guar gum concentration was developed. This fracturing fluid had guar gum concentrations of 0.30%-0.35%, with its properties remained stable between 120-130℃. This fracturing had the advantages of complete gel breaking(η<8 mPa·s), low residue(117 mg/L), slight damage to reservoir permeability(<10%), and good rheology. It was successfully used in fracturing operation in the Well Tahe535.
Application of Molecular Simulation Technology in Drilling Fluid Research
YANG Fan, YANG Xiaohua, KONG Yong, DONG Xiaoqiang
2015, 32(5): 89-93. doi: 10.3969/j.issn.1001-5620.2015.05.022
As an oncoming computational chemistry technology, molecular simulation has found many more applications in computeraided molecular design, structure solution, and physical property prediction, and is widely used in petroleum industry, chemical engineering, food, pharmacy, and aviation etc. The application of molecular simulation in the field of drilling fluids, such as the mechanism of clay hydration and swelling, design of clay stabilizer, drilling fluid surfactants such as foaming agent and emulsifier, as well as high molecular weight polymers such as PAM, starch, lignin, dendrimer, and environment-responsive polymer are introduced. Using the molecular mechanics and molecular dynamics, with the aid of analogy computation of the properties of a single molecule or a system of molecules, such as their structure, conformation, thermo-dynamic characteristics and phase-transition etc., drilling fluids can be studied in these area such as construction of theoretical model of additives, molecular structure design, optimization of synthetic route of additives, presentation of working process of additives, and the analysis of experimental phenomena. Difficulties that may be encountered and the prospect of the application of molecular simulation in the studies of drilling fluid additives are also discussed in this paper.
Discussion on Determination of Yield of Bentonite
CAI Lishan, YANG Jian
2015, 32(5): 94-97. doi: 10.3969/j.issn.1001-5620.2015.05.023
Yield is an important parameter of bentonite.The determination of this parameter is quite complex and time consuming. Lack of known properties of clay samples and difference in laboratory operator's skills play an important role in the success of the determination. Repeatability of determining the yield of bentonite is poor, and different persons measuring the yield of the same bentonite sample may give different results. It has been found that these problems can be mitigated or even eliminated using Excel's trend line fitting function. Validation of experiment data proves that clay suspension formulated with bentonite determined by the "trend line fitting" function has Fann35 readings closely agree with theoretical values, indicating that this method of yield determination is accurate and efficient.
Well Cementing Technology for Well Yangtan-1 with High Circulation Pressure
ZHONG Fuhai, HE Shuhua, GAO Fei, FEI Zhongming, LIU Zhentong, WANG Fuchang, ZHU He
2015, 32(5): 98-100. doi: 10.3969/j.issn.1001-5620.2015.05.024
High circulation pressure prior to well cementing has long been a problem that remains unsolved. In cementing the well Yangtan-1, after running liner strings and circulating for 51 h, flow rate was still so low, only 0.9 m3/min, but the pump pressure was unreasonably high, up to 22 MPa. The well finally had to be cemented at high circulation pressures. Several measures were adopted to avoid accidents during cementing, such as using high strength surface manifolds, improving the rheology of drilling fluid and cementing fluids (prepad fluids, spacers, and cement slurries etc.), minimizing the volume of redundan t (additional) cement slurries, reasonably prolonging the thickening of cement slurry, and displacing at low pump rates. CBL-VDL logging data after 48 h show that of all the cemented length of the wellbore, 7% cemented are perfect, 52.5% cemented acceptable, and the rest 40.5%, are poorly cemented. Depth of the cement top in the annular space and the quality of the cementing job satisfy the needs for subsequent well operation.