钻井液与完井液

Abstract:
Organic salts are presently used to improve the high temperature stability of solids-free drilling fluids, which have higher density because of the presence of organic salts. Higher density plays a negative role in the protection of deep high temperature lowpressure reservoirs. A solids-free high temperature drilling fluid, WGX, was recently formulated with a newly developed viscosifier SDKP, and a series of selected additives such as antioxidant, filter loss reducer, lubricant and inhibitive agent. WGX had a density of 1.02 g/cm³ and remained stable at 190℃. Performance evaluation showed that WGX had good high temperature rheology and good carrying capacity at high temperature. Permeability test gave a percent permeability recovery of greater than 90%. The rheology of WGX remained satisfactory even when contaminated with 5% NaCl or 10% clays. Percent rate of swelling of cores tested with WGX was only 7.22%, and hot rolling test showed a percent recovery of shale samples of 89.33%. WGX tested on an extreme lubricity tester showed that the extreme frictional coefficient was only 0.085.

Study on Static Viscoelastic Characteristics of Drilling Fluid Using Micro-rheology

ZHAO Xionghu, HAN Xiao, XU Tongtai

2015, 32(1): 7-9,13. doi: 10.3969/j.issn.1001-5620.2015.01.002

Abstract(666) PDF (6845KB)(213)

Abstract:
The changing process of the viscoelasticity of drilling fluid at static condition was studied using micro-rheology technology. Drilling fluids of different compositions were formulated and tested on their viscoelasticity with Rheolaser^TM after agitating at high shear speeds. Laboratory study found that it is the network formed in oil base drilling fluids that suspend barite particles. Oil base drilling fluid lost its network structure at high shear speeds and resumed the network if allowed to stand quiescent for enough time. The dissipation factor of the network, an indicator of the drilling fluid's ability to resume its original network structure, was decreasing with time, meaning that the settling speed of barite particles was becoming slower. Drilling fluids with poor behavior will lose part of their viscosity and relaxation time, leading to instability in their network structures and fast settling of barite particles. Organophilic clay and gelling agents having the ability to reinforce the micro structure of drilling fluid, when added to a certain amount, accelerate the resumption of the network in drilling fluid. Micro-rheology can be used to describe the changing process of the network formed in drilling fluid, and hence plays an important role in studying and understanding the complex performance changing of drilling fluid.

Laboratory Study on Ultra High Temperature Water Base Mud

XU Jie, WU Xiaoming, ZHU Yongyi, Chikhotkin V. F., XU Mingbiao, WU Chuan, ZHENG Wenlong

2015, 32(1): 10-13. doi: 10.3969/j.issn.1001-5620.2015.01.003

Abstract(673) PDF (1611KB)(273)

Abstract:
A high temperature water base drilling fluid was formulated with sodium bentonite and attapulgite, and a high temperature water-in-oil stabilizer, MG-H2 which is synthesized through emulsion polymerization. Laboratory evaluation of the drilling fluid showed that, after aging at 240℃, the drilling fluid still retained satisfactory rheology and filtration properties. It had good inhibitive capacity and was resistant to contamination caused by the introduction of 10% clay, or a combination of 5% NaCl and 1% CaCl₂. It also had good lubricity at high temperature. The formulation of this high temperature drilling fluid lays the foundation for the formulation of an ultra-high temperature drilling fluid, say, 260℃, for the drilling of the Well Songke-2.

Study and Application of Revers Osmosis Low Free Water Drilling Fluid

CHEN Jinxia, KAN Yanna, CHEN Chunlai, LU Shuqin, WANG Jian

2015, 32(1): 14-17. doi: 10.3969/j.issn.1001-5620.2015.01.004

Abstract(680) PDF (2918KB)(264)

Abstract:
Plugging material of nanometer and micron in size were introduced into the formulation of reverse osmosis low free water drilling fluid to solve the borehole wall instability problem in Block Nanpu. A semipermeable membrane near the borehole formed by the plugging material, can, when in combination with bonding water, reduce the water activity of the drilling fluid, which in turn, resulted in reverse osmotic pressure, balancing the pressure of the drilling fluid column and capillary pressure existing in shale formations. Shale formation stability can be improved by this process. HSM, a micelle agent, and HGW, a borehole wall strengthening agent, were used to formulate the reverse osmosis low free water drilling fluid. HSM, when dissolved in water, assumes spheroidal, laminar, or rod shapes with sizes ranging between 1 nm and 100 nm. HSM, with its hydrophilic groups adsorbed onto the surface of borehole wall, has its hydrophobic groups entangled with each other to form a protection membrane against invasion of free water from drilling fluid to enter into the formation. HGW, a hydrophobic submicron emulsion, protect borehole wall by forming a hydrophobic layer on the surface of the borehole wall. By adding 3% HGW and 2% HSM, the membrane efficiency can be increased from 0.11 to 0.3, and to 0.50 if 20% bonding agent was further added. Laboratory test showed that this drilling fluid was similar to oil base drilling fluid in terms of inhibitive capacity, lubricity, and reservoir protection. Two wells, Nanpu2-35 and Nanpu4-65, drilled with this drilling fluid had no borehole instability problems, with gauge holes obtained. Compared with offset wells, drilling fluid density was reduced from 1.26 g/cm³ to 1.20 g/cm³, and ROP was increased by 49.26%.

Permeability Impairment and Reservoir Protection for Tight Sand Gas Reservoir in Block Dina-3

TENG Xueqing, ZHANG Jie, ZHU Jinzhi, WANG Shuangwei, ZHAO Zhiliang, ZHAO Ze

2015, 32(1): 18-21. doi: 10.3969/j.issn.1001-5620.2015.01.005

Abstract(606) PDF (1629KB)(250)

Abstract:
The tight sands gas reservoir in Block Dina-3 is characteristic of low porosity, ultra-low permeability, clastic rock, low initial water saturation, severe inhomogeneity, developed fractures, and high clay content. The previously used potassium polymer sulfonate drilling fluid posed damage to the reservoir. By analyzing the mechanism of reservoir damage for the Block Dina-2 and the Block Dina-3, it was believed that the potassium polymer sulfonate drilling fluid caused water sensitivity, stress sensitivity, mud losses, capillary effect and phase trap damage to the reservoir. The potassium polymer sulfonate drilling fluid was modified with lost circulation material water block preventer that can be removed by acid treatment. The new drilling fluid had good rheology, low filter loss and excellent reservoir protection capacity.

Study on Solids-free High Temperature Drilling Fluid Used in Wenchang Gas Field

ZHANG Chong, REN Guanlong, ZENG Chunmin, YU Yi, WU Jiang

2015, 32(1): 22-25,29. doi: 10.3969/j.issn.1001-5620.2015.01.006

Abstract(645) PDF (1742KB)(219)

Abstract:
Three blocks, Wenchang 9-2, Wenchang 9-3 and Wenchang 10-3, are gas fields located in the Zhujiangkou Basin. Gas reservoirs in this basin are characteristic of high temperature (165℃) and low permeability. Laboratory studies had been performed on PRD, a solids free drilling fluid used by CNOOC in oil and gas well drilling, to improve its high temperature performance. PRD was optimized with high temperature filter loss reducer, high temperature viscosifier, high temperature drilling starch, water block preventing agent, ultrafine calcium carbonate, polyamine, and high temperature stabilizer. The new formulation was stable at 170℃, and percent shale core sample recovery rate was 95.3%. Return permeability of fluid-contaminated cores was greater than 90%, while the mud cake formed on the cores was very easy to remove. The selected water block preventer, when added at a concentration of 2%, reduced the surface tension of the gas-liquid interface of mud filtrate to less than about 30.0 mN/m, and that of oil-water interface to less than 5 mN/m, a very good water block preventer for reservoir protection. This new formulation is suitable for use in offshore drilling where low permeability and high temperature reservoirs are horizontally drilled.

Molecular Structure and Performance of Oligomeric Amine Shale Inhibitor

GUO Wenyu, PENG Bo, CAO Weiping, ZHANG Longjun

2015, 32(1): 26-29. doi: 10.3969/j.issn.1001-5620.2015.01.007

Abstract(831) PDF (4953KB)(265)

Abstract:
Oligomeric amines were investigated for the effect of their molecular structures on their inhibitive capacity, API filter loss and adsorption behavior. The presence of hydrocarbon and amino groups in the oligomeric amine molecules results in an increase in the API filter loss of a mud treated with oligomeric amine, although the effect of amino group is weaker than that of the hydrocarbon group. The ether group and carboxymethyl group reduce the filter loss of a mud. Amino group is the strongest adsorption group, followed by ether group and hydrocarbon group. Carboxymethyl negatively affect the adsorption of mud additives. All the oligomeric amines, when adsorbed, form single layer on the surface of clay particles, which is beneficial to the formation of a minimum spacing between the unit layers of clay, thereby preventing clay from swelling. A polyamine additive, RZPA, made from polyetheramine D230, the best amine shale inhibitor, was used in drilling the well Jiangsha33-8 in Deyang, Sichuan. Good inhibitive capacity was found when drilling water sensitive shales. Hot rolling test showed that RZPA had percent recovery of shale samples between 73% and 81%.

Development and Evaluation of a Dual Adsorption Base Lubricant SR-1

SHI Peiqian, WANG Qing, ZHANG Hongwei, WANG Shanju, LI Baohui

2015, 32(1): 30-33. doi: 10.3969/j.issn.1001-5620.2015.01.008

Abstract(547) PDF (5002KB)(190)

Abstract:
A lubricant, SR-1, was developed by introducing dual adsorption base hydrophilic group into the molecule of a high molecular weight fatty acid, which would strengthen the adsorption of SR-1 onto the friction interface, and weaken the influences of other additives on the lubricity of SR-1. Laboratory study showed that SR-1 is resistant to salt contamination and high temperature (220℃). Polymer sulfonate mud treated with SR-1 reduced the extreme pressure coefficient of friction to less than 0.06, (percent decrease by 80.24%). SR-1 should be used at pH of not less than 12, otherwise the efficiency of SR-1 will decrease. SR-1 has good compatibility with other mud additives, and reduces filter loss to some extent. It can be used in deep well, directional well and horizontal well for the requirement of low friction.

Study on Borehole Collapse Drilling Shiqianfeng and Shihezi Formations in Yanchang Gasfield

ZHENG Weijuan, XU Tongtai, DONG Xiaojun, WANG Hailiang, ZHANG Yongli, WU Beibei

2015, 32(1): 34-37,41. doi: 10.3969/j.issn.1001-5620.2015.01.009

Abstract(666) PDF (17827KB)(200)

Abstract:
Borehole collapse had always been encountered when drilling the Shiqianfeng and Shihezi formations in Yanchang gas field. Laboratory study has been conducted to determine the mechanism governing the borehole wall instability. By measuring the geo-stress, mechanical characteristics of the rocks in formations where borehole collapse was encountered, mineral composition, and physic-chemical properties of the formations, it was found that the Shiqianfeng and Shihezi formations are composed of hard and brittle rocks, is capable of being dilatant at stresses that are far below the peak stress. Fluctuation of pressure forced the micro fractures near the wellbore to extend and converge, forming an instable high permeability zone. Study found that no high tectonic stress exists in Yanchang gas field, but formation reversion and fracture are quite developed. The formations drilled are in late diagenesis, and the mudstones have high clay content, making them moderate to strong swelling. Drilling fluid used in drilling these formations should have good inhibitive capacity. Low mud weight, less than the density equivalent of collapse pressure of formation, caused the formation to collapse. Long period of time for the borehole to be "empty" (with no drill tools in the hole) led to increasing collapse pressure of the formations, aggravating borehole collapse. Poor sealing and plugging ability of the drilling fluid, which cannot effectively seal and plug micro fractures on the borehole wall, was another cause of borehole collapse.

Mechanism and Strategy to Deal with Borehole Instability of Hard and Brittle Shales in Halahatang Oilfield

LIU Fengbao, SHAO Haibo, ZHOU Zhishi, ZHANG Huanqing, CHEN Yongheng

2015, 32(1): 38-41. doi: 10.3969/j.issn.1001-5620.2015.01.010

Abstract(578) PDF (1688KB)(277)

Abstract:
Mechanism and strategy to deal with borehole instability of the Triassic System and Silurian System hard and brittle shale in Halahatang Oilfield were studied both from mechanics and physic-chemistry. The study shows that for the formations drilled, the magnitudes of the three principal stresses are in the following order: σ_Z > σ_H > σ_h, and shales in the Triassic System are more easily becoming mechanically instable than those in the Silurian System. Shales in the Triassic System have ion exchange capacity, montmorillonite content, colloidal content and percent rate of swelling of 25.4 mmol/100 g, 36.3%, 76.4% and 23.2%, respectively, meaning that the shales have great surface hydration capacity and are easy to become physicochemically instable. In field operations of Well I and Well II, by increasing mud density and enhancing the inhibitive capacity of mud in the Triassic System, and by improving the plugging capacity of mud in the Silurian System, borehole instability was almost eliminated.

Development and Appraisal of Computer Software for Optimization of Particle Size of Temporary Plugging Agent

ZHAO Zhiqiang, MIAO Hailong, GENG Tie

2015, 32(1): 42-45. doi: 10.3969/j.issn.1001-5620.2015.01.011

Abstract(619) PDF (6153KB)(208)

Abstract:
Optimization of the particle size distribution of temporary plugging agent plays a key role in reservoir protection. An ideal packing model for temporary plugging agent particle size optimization was developed based on the Alfred Model, and a software was developed on the VB.NET platform. This software calculates the optimized particle size distribution using the parameters of the target formation. The relationship between binary and ternary particle size compatibility and filter loss was examined through PPT experiment, and the inverse correlation of the two was verified. Positive correlation between the degree of match and permeability recovery was verified through laboratory experiment on artificial cores of 0.38 μm²-0.42 μm². Laboratory experiment showed that particle sizes optimized using the developed software effectively reduced reservoir damage, and the optimization results can be used in well completion and workover designs.

Optimization of Flocculation Performance of PRD Drilling Fluid for Fine Solids

BAI Chaofeng, HUANG Kaiwen, ZHANG Chong, YU Yi, YUE Qiansheng, WU Hongte

2015, 32(1): 46-48. doi: 10.3969/j.issn.1001-5620.2015.01.012

Abstract(567) PDF (3552KB)(195)

Abstract:
Particle size distribution was tested for barite, ultra-fine calcium carbonate, bentonite and shale cuttings (from reservoir section) dispersed in liquids, and their effects on the permeability of reservoir formations were evaluated. It was found that the bentonite and shale cuttings, which contain large numbers of micron and submicron particles, blocked the flow channel of the cores. Based on the test results, a flocculant, PL-1, was selected to flocculate these fine solids. In laboratory core flooding test, the PRD drill-in mud (for low-permeability reservoir drilling) treated with 0.1% PL-1 gave a percent permeability recovery of 79.7%, while PRD drill-in fluid not treated with PL-1 gave a percent permeability recovery of 66.9%, showing the efficiency of PL-1 in reservoir protection. PL-1 also helped reduce the filter loss of PRD.

Study and Application of Rigid Wedging Mud Loss Control Under Pressure

HOU Shili, HUANG Daquan, YANG Hewei, LIU Guangyan, LI Shuan, WANG Lukun, SUN Shuang, WANG Xiaofang

2015, 32(1): 49-52. doi: 10.3969/j.issn.1001-5620.2015.01.013

Abstract(624) PDF (530KB)(228)

Abstract:
The rigid wedging mud loss control under pressure is a technology in which rigid lost circulation material (LCM), expandable or expandable LCM, and low permeability LCM are employed to bridge the mud loss channels. It involves bridging, wedging and filling in the fractures and pores of formation to increase the circumferential stress of formation, hence enhancing the pressure bearing of the formation. LCM slurries for mud loss control under pressure were formulated with optimized particle size distribution determined by SAN-2 engineering theory. The rigid LCM was also compounded with other LCM to verify their performance in mud loss control. The experiments showed that LCM slurries containing compounded rigid LCM, expandable LCM and low permeability LCM promptly bridged and filled the fractures and formed low permeability packing with pressure bearing of 7 MPa. In field application of this technology in 33 wells, success rate of mud loss control was increased remarkably, and the quantity of LCM slurries was reduced.

Application of Microtox Biological Toxicity Testing Technique in Drilling Fluid Analysis

ZHU Hongwei, LIU Xiaodong

2015, 32(1): 53-56. doi: 10.3969/j.issn.1001-5620.2015.01.014

Abstract(786) PDF (3465KB)(211)

Abstract:
This paper introduces the testing instrumentation, principles and testing method of Microtox, a biological toxicity testing technique. The EC₅₀ values of some mud additives and drilling fluid formulations were tested using the Vibrio fischeri as the testing bacteria. An onsite fast testing method was presented using Microtox technique. Laboratory experiments showed that drilling starch, XC, polyhydric alcohols, as well as natural high molecular weight polymers are nontoxic. Sulfonated phenolic, lignite, asphaltene, FCLS and the so-called tri-sulfonates drilling fluids have EC₅₀ values that are far less than the national standard of 30,000 mg/L. AMPS copolymers and synthesized high temperature polymer drilling fluids are nontoxic. Microtox technique provides two toxicity test methods for discharged drilling fluid in offshore drilling, a qualitative method and a quantitative method. Meanwhile this method can be used as a means of evaluating environmentally friendly drilling fluid.

A Novel Instrument for Evaluating Start-up Pressure of Special Gel ZND

WANG Pingquan, ZHU Tao

2015, 32(1): 57-59,64. doi: 10.3969/j.issn.1001-5620.2015.01.015

Abstract(528) PDF (5792KB)(214)

Abstract:
ZND, a special gel has recently found a wide use in controlling mud losses. This paper discusses a novel instrument used for the evaluation of ZND, and a method of measuring the start-up pressure of ZND-liquid level-pressure curve method. By plotting the liquid level versus pressure, this high-precision instrument can be used to determine the start-up pressure of ZND in simulated formation conditions, and the performance of gels at the same start-up pressure.

Laboratory Study of Viscoelastic Isolation Additive for Use in Oil Well Cementing

LV Bin

2015, 32(1): 60-64. doi: 10.3969/j.issn.1001-5620.2015.01.016

Abstract(497) PDF (6546KB)(214)

Abstract:
A new cementing additive, DQV, was prepared making the use of polymer's viscoelasticity. DQV is an additive used in cement slurry for better isolating formation and casing string. When mixed with cementing slurry, the mixture can render the annular space very good sealing, both efficient and flexible. Cement slurry treated with DQX had anti-migration capacity that was ten times of the original class G cement slurry, and the overall permeability of the set cement was reduced by two orders of magnitude. Meanwhile, the thickening time of the cement slurry was adjustable. The mobility and free water of the cement slurry were 25 cm and 0, respectively. Field application program for the cementing job using DQV was also studied for better anti-migration and isolation capacities of the cement slurry.

Pressure Activated Sealant

GUO Limei, XIAO Miao, LIU Juxiang

2015, 32(1): 65-68. doi: 10.3969/j.issn.1001-5620.2015.01.017

Abstract(699) PDF (5159KB)(239)

Abstract:
A pressure activated sealant was developed to overcome leaking of oil well pipework. The sealant was formulated with butyronitrile latex as base additive, CH₃COONa, MgSO₄ and NaCl as activators, Gemini1231 and Gemini1631 as terminators and sodium montmorillonite as stabilizer. Laboratory study showed that this sealant only became coagulated at leaking sites where there were differential pressures, otherwise maintained in mobile state. The sealant worked at temperatures between -20℃ and 120℃ and had particle sizes between 0 μm and 1,000 μm, or bigger. In a simulation test with 139.7 mm tubing in which the thread was damaged, when leaking rate was 600 mL/min, the leaking was stopped after applying the sealant and waiting for 60 s. After reparation, no leaking was found for the tubing under 40 MPa of water pressure and 35 MPa of nitrogen gas pressure, satisfying the requirement of industrial standard.

Study and Application of Ultra-high Density Cement Slurry

YAO Zhixiang

2015, 32(1): 69-72. doi: 10.3969/j.issn.1001-5620.2015.01.018

Abstract(610) PDF (1533KB)(282)

Abstract:
An ultra-high density cement slurry was formulated with iron powder (density 7.0 g/cm³) of different particle sizes 0.154 mm, 0.076 mm and 0.03 mm in a ratio of 3:2:1, and latex suspending agent and liquid additives. This cement slurry has density of 2.82 g/cm³ and good suspending capacity, with density difference between the top and the bottom slurry of equal to or less than 0.028 g/cm³. At 30℃ and ambient pressure, the set cement has compressive strength of 14 MPa after aging for 48 h. API filter loss can be controlled to less than 50 mL. SPN of the cement slurry is equal to or less than 3. This high density cement slurry was used successfully in the cementing operation of well Wen72-421, in combination with a special cementing technology for high density cement slurry.

Experimental Analysis of Influencing Factors on the Mechanical Deformation of Set Cement

HUANG Haihong, TANG Shizhong, YU Fen, ZHAI Tengfei, GONG Yu, HU Xing

2015, 32(1): 73-76. doi: 10.3969/j.issn.1001-5620.2015.01.019

Abstract(490) PDF (2048KB)(249)

Abstract:
This paper discusses the calculation of the deformability of set cement using experimental data, which are presently rare, obtained under different circumstances such as cement slurry formulation, experimental temperature, confining pressure, curing time and thickness of cement sheath. It shows that the elastic modulus of cement sheath is reduced by adding elastic and tough materials, and that a better mechanical deformability of cement sheath is obtained by adding latex than by adding cellulose. The elastic modulus of set cement decreases with an increase in curing temperature, and the total deformability of the cement sheath, at the same time, increases. An increase in confining pressure weakens the deformability of the set cement. The mechanical deformability of the set cement sheath, to some extent, increases with time. The thickness of the cement sheath has no effect on the property of the set cement, but a decrease in cement sheath increases the deformability of the set cement, by 85.5% at the most under the prevailing downhole condition presented in this paper.

Effect of Magnesia Whisker on Mechanical Property of Set Cement

LOU Chenyang, YAO Xiao, GU Guangwei, WANG Ping, ZHOU Shucheng

2015, 32(1): 77-80. doi: 10.3969/j.issn.1001-5620.2015.01.020

Abstract(610) PDF (5033KB)(203)

Abstract:
Study was conducted on the effect of MBW, a magnesia whisker, on the basic performance of cement slurry and the mechanical property of the set cement, with the aid of XRD, MIP and SEM. It was shown that addition of 1%-5% MBW into oil well cement slurry generally had no effect on the density and thickening time of the slurry. The mobility of the slurry, however, was reduced with the addition of MBW, but can be improved by the treatment with USZ, a drag reducer. With the addition of MBW, the compressive strength and flexural strength of the set cement were apparently enhanced. At 80℃, the 1 d, 3 d, 7 d and 28 d compressive strengths of a cement slurry treated with 4% MBW were 8.3%, 15.4%, 21.5% and 18.8% higher than that of the base cement slurry, respectively; the 1 d, 3 d, 7 d and 28 d flexural strength of the cement slurry (containing 4% MBW), on the other hand, were 9.4%, 19.4%, 13.1% and 0.3% higher than that of the base cement slurry. MBW is an inert additive, which fills in the detrimental pores in set cement, hence improving the tightness thereof. As a kind of micro fiber, MBW plays a role in hardening and toughening set cement through bridging, pulling, stripping and breaking.

The Synthesis of and Study on AA/SSS/APO Terpolymer Retarder

YAN Siming, LI Xingwu, GAO Jin, WANG Fuhui, LIAO Yongmei

2015, 32(1): 81-83. doi: 10.3969/j.issn.1001-5620.2015.01.021

Abstract(627) PDF (1685KB)(269)

Abstract:
Using acrylic acid (AA), sodium p-styrene sulfonate (SSS) and an alkylene monomer (with long hydrophilic chain) (APO) as raw materials, a terpolymer retarder, BH, was synthesized through water solution polymerization, with ammonium persulfate as initiator. Using single factor analysis, the optimum molar ratio of these monomers was determined to be 1 (AA):1 (SSS):0.1 (APO), the mass fraction of monomer's concentration 30%, the concentration of initiator, 4% (m/m), pH 5, and reaction time at 80℃, 14 hours. The molecular structure of the polymer was characterized by IR spectroscopy. Cement slurries treated with BH were studied on their retarding performance, temperature sensitivity, rheology, free water and compressive strength. It showed that the BH can be used in a wide range of temperatures (90-170℃), and is not sensitive to temperature changes. At BH concentration of 2.75% and 170℃, the BH-treated cement slurry has a thickening time of 356 min. The addition of BH improves the rheology of cement slurry, and has little, if any, effect on the strength of set cement. Cement slurries treated with BH can be used in salt concentrations of up to 16%.

Development and Performance of Solid Boron Crosslinking Agent

ZHANG Danian, ZHAO Chongzhen, ZHANG Suobing, ZHAO Mengyun, SU Changming, LIU Song, ZHENG Chenggang

2015, 32(1): 84-86. doi: 10.3969/j.issn.1001-5620.2015.01.022

Abstract(553) PDF (2475KB)(208)

Abstract:
This paper discusses the development and performance of a solid inorganic boron crosslinking agent, G-CYS, for use in fracturing, and four fracturing fluids for use at 100℃, 120℃, 140℃, and 160℃, respectively. The four fracturing fluids at different temperatures have good high temperature stability and shear thinning performance, and their gels are thoroughly broken to low viscosity fluids. At 160℃, the fracturing fluid has a viscosity of 120 mPa·s after shearing 2 min at 1000 s^-1, or 120 min at 170 s^-1, satisfying the needs for medium or high temperature fracturing. The dissolution rate of the solid boron crosslinking agent can be controlled with pH and temperature, thereby adjusting the time for cross linking. The fracturing fluid, after completion of crosslinking, will not dewater for more than 60 min, which is satisfactory for field use, where job delay inevitably leads to dewatering and quality-deterioration of fracturing fluids.

A New Oil Soluble Temporary Plugging Agent

WANG Shengpeng, TANG Bangzhong, CUI Zhouqi, ZHAO Anjun, WU Gang, LU Hao

2015, 32(1): 87-89. doi: 10.3969/j.issn.1001-5620.2015.01.023

Abstract(600) PDF (1968KB)(291)

Abstract:
A new temporary plugging agent, ZD-150, was developed to overcome the high operational pressure and high risk of sand plugging in fracturing job in high closure stress reservoirs. ZD-150 can stand temperatures to 120℃, and has oil solubility of greater than 95% in 48 h, and acid solubility of less than 5% in 24 h. Suspension of 0.2% guar gum solution containing 15% ZD-150 remains stable for 12 h, with no sedimentation. ZD-150 has high compressive strength and good temporary plugging performance. The application of ZD-150 in 10 wells showed that, by combining with ceramic powder, the turnaround efficiency of the operation was enhanced by 1.5 times, and even by 2.1 times after further modification. ZD-150 is a new additive for use in increasing the complexity of fractures in SRV fracturing.

Study and Application of Small Clearance Cementing Technique for Casing Sidetracking Slime Hole

ZHONG Fuhai, WANG Helin, SHAN Baodong, ZHANG Ruguang, SUN Wanxing, JIANG Shiwei, LI Huan

2015, 32(1): 90-92. doi: 10.3969/j.issn.1001-5620.2015.01.024

Abstract(557) PDF (2183KB)(195)

Abstract:
Casing sidetracking of production casing string is an important means of bringing back to life abandoned oil wells and enhancing oil recovery. Casing sidetracking has the advantage of cost efficient and time saving, but small annular space clearance increases the friction of cement slurries flowing upward, thus fracturing the formation and resulting in losses of cementing slurry. Another disadvantage of cementing the sidetracking well is the big eccentricity of casing string, which will result in channeling of cement slurry. To solve these problems, a low friction coefficient low density cement slurry was developed. By reducing the density of the cement slurry, the hydrostatic pressure exerted by cement slurry column was reduced. In field operations, cement job quality was remarkably improved. It is proven to be a feasible cementing technology for use in Huabei Oilfield.

Drilling Fluid Technology to Enhance ROP in Azraq, Sudan

CHEN Bo, ZHAO Houchun, XU Xintong

2015, 32(1): 93-96. doi: 10.3969/j.issn.1001-5620.2015.01.025

Abstract(572) PDF (2108KB)(180)

Abstract:
Optimization of drilling fluid property was studied in laboratory to aim at rate of penetration (ROP) in Azraq area in Sudan. The optimized drilling fluid had filter loss of 6-8 mL, plastic viscosity (PV) of 15-20 mPa·s, yield point (YP) of 10-15 Pa and an YP/PV ratio of 0.75 Pa/mPa·s. A clay-free silicate drilling fluid with these properties was formulated through laboratory experiment. With this drilling fluid the ROP was increased from 6-8 m/h to 12-18 m/h in the Abu Gbura formation. The well Azraq K-9 was completed in the shortest period of time in this area.

Competent Authorities：China National Petroleum Corporation Ltd

Sponsored by：CNPC Bohai Drilling Engineering Co. LtdPetroChina Huabei Oilfield Company

Editor-in-Chief：Shi-chun Chen

Address： Editorial Department of Drilling Fluid and Completion Fluid, Bohai Drilling Engineering Institute, Yanshan South Road, Renqiu City, Hebei Province

Postcode： 062552

Tel：（0317）2725487　2722354

E-mail： zjyywjy@126.com

CN13-1118/TE

ISSN1001-5620

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