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Wu H.,Research Institute of Oil and Gas Engineering | Kong C.,Research Institute of Oil and Gas Engineering | Yi X.,Chengdu University of Technology | Zhang H.,Research Institute of Oil and Gas Engineering | And 2 more authors.
Drilling Fluid and Completion Fluid | Year: 2016

Acid-corroded wormholes generated in acid fracturing of carbonate rocks play an important role in flow channel communication. A quantitative characterization of the surface of the fracture planes before and after acid corrosion has not yet been found. The acidcorroded wormholes can be quantitatively characterized with a 3D laser scanner which scans the surface of the fracture planes before and after filtration of acid and numerically processes the data obtained. Studies show that the isogram and the 3D plots of the fracture planes give a clear picture of the acid-corroded wormholes. The dimensions of different spots in a wormhole can be obtained from the isogram and 3D plots of the fracture spacings. The number and the proportion of the cloud points of the different spacings in acidcorroded wormholes can be obtained from the matching histogram of the fracture planes and the histogram of the spacing distribution of the fractures. Using these data, the volume of the acid-corroded wormholes can be calculated, providing guidance to acid fracturing design. © 2016, The Editorial Board of Drilling Fluid & Completion Fluid. All right reserved.


Li N.,Research Institute of Oil and Gas Engineering | Wang Y.,China University of Petroleum - East China | Zhang S.,Research Institute of Oil and Gas Engineering | Li J.,Research Institute of Oil and Gas Engineering | And 3 more authors.
Drilling Fluid and Completion Fluid | Year: 2016

The target zone of the block B in Tarim Basin is the Cretaceous Bashijiqike Formation. The depth of the wells drilled is greater than 6, 000 m, and the reservoir rocks are tight, with porosity ranging from 1.0% to 9.4%, and permeability from 0.011×10-3 to 8.56×10-3 μm2. The porosity has poor relationship with permeability. The highly heterogeneous reservoir rocks have poorly developed pores, low permeability, developed fractures, high capillary forces, high clay contents, and are very easy to be affected by water blocking during well completion and fracturing. Analyses of water blocking based on the geological features of the reservoir rocks in this area indicate that the capillary water accounts for almost half of the volume of the pores, leading to highly difficult gas flow in the porous media. Using the Model SRT-II low permeability sensitivity tester, formation damage by water blocking is macroscopically analyzed through core flow experiment. Using NMR transverse relaxation time spectrum, formation damage by water blocking is microscopically analyzed. The analyses show that water blocking caused the permeability of the reservoir rocks to be reduced by 99%, and more than 90% of the water blocked in this area, mainly in the 0.01-250 nm pores. Based on the research, water blocking remover SATR0-1 and HUL were chosen and their performance studied through capillary imbibition, NMR examination, and permeability experiments. It was concluded that SATR0-1 and HUL can effectively reduce capillary forces and invasion depths by imbibition, and are helpful to liquid flowback through micro pore throats. © 2016, The Editorial Board of Drilling Fluid & Completion Fluid. All right reserved.


Xiaofeng S.,Northeast Petroleum University | Kelin W.,Northeast Petroleum University | Tie Y.,Northeast Petroleum University | Yang Z.,Research Institute of Oil and Gas Engineering | And 2 more authors.
Open Petroleum Engineering Journal | Year: 2013

Complex structural wells are widely used in the development of marine oilfield, old oilfield and low permeable oilfield. However, poor hole cleaning is often occurred in the highly-deviated sections and horizontal sections of the complex structural wells, which affects rate of penetration and downhole safety. The methods to study cuttings transport can be normally divided into four types: 1) experimental observations, 2) CFD simulations, 3) theoretical correlations and models and 4) field tests. Experimental observations and CFD simulations are mainly used to analyze the effects of different parameters on hole cleaning and obtain some valuable data. Theoretical models and correlations are mainly applied to calculate cuttings bed height, critical velocity and etc to provide the guidance for the design of hydraulic parameters. The accuracy of the first three types are checked by field tests. In this paper, the effects of flow rate, inclination, mud rheology, drillpipe rotation and other factors on hole cleaning, and some typical correlations and models were briefly reviewed before 2000 years, and some new research findings were detailedly addressed. In addition, CFD simulations also were introduced. Although major improvements have been achieved in the past several decades, building a comprehensive and proven model requires much more experimental researches, CFD simulations, in-depth theoretic studies and field tests due to the complexity of cuttings transport under multi-factor interactions. © Xiaofeng et al.


Teng X.,Research Institute of Oil and Gas Engineering | Zhu J.,Research Institute of Oil and Gas Engineering
Drilling Fluid and Completion Fluid | Year: 2015

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. ©, 2015, North China Petroleum Administration Drilling Technology Research Institute. All right reserved.


Li N.,Research Institute of Oil and Gas Engineering | Li J.,Research Institute of Oil and Gas Engineering | Zhu J.,Research Institute of Oil and Gas Engineering
Drilling Fluid and Completion Fluid | Year: 2015

The "zero potential" theory was used to optimize the formulation of drilling fluid used in deep well and ultra-deep well drilling in Tarim Basin to overcome shale swelling and pipe sticking in top formations and difficulties in mud property maintenance in lower deep formations. Using optimized cationic polymers, a "zero potential" water base drilling fluid was formulated. This drilling fluid had high concentration of cations, and clay particles of high zeta potential, almost equal to or slightly higher than the zeta potential of the "in-situ" drilled cuttings, meaning that the potential difference between the formation and the drilling fluid is "zero", hence greatly mitigating the possibility of borehole wall instability caused by frequent migration of electric charges between formation and drilling fluid. This drilling fluid also had good rheology and filtration property, and was resistant to contaminations from the introduction of salt, calcium and clays, especially at high temperatures in deep and ultra-deep wells. The "zero potential" drilling fluid had been used in 20 wells in Tarim Basin. Compared with conventional water base drilling fluids, total time spent in dealing with drilling fluid-related downhole troubles was reduced by 10.2%, ROP increased by 14.9%, and drilling time reduced by 9.8%. The successful application of the "zero potential" drilling fluid in Tarim Basin provides a means of fast, safe and efficient drilling deep wells, and enriches and further develops the idea of "zero potential" drilling fluid. ©, 2015, North China Petroleum Administration Drilling Technology Research Institute. All right reserved.

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