Petroleum Exploration and Development

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Zhao Wenzhi; Bian Congsheng and Xu Zhaohui

. 2013, 40(4): 2-0.

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Both Sulige gas field in the Ordos Basin and Xujiahe gas field in the central Sichuan Basin are large low-porosity and low-permeability gas fields composed of conventional and unconventional gas accumulations, and are typical cases of low-grade natural gas accumulations in China. Studies show there are both similarities and differences between these two fields in terms of forming condition, mechanism and distribution. The similarities include: (1) large-scale development of accumulation conditions and close source-reservoir contacts provide basis for large-scale accumulations; (2) large-scale energy storage during source kitchen burial and large-scale gas expulsion during uplift provide important conditions for large-scale natural gas accumulation; (3) coexisting volume flow and diffusion flow give rise to the co-existence of conventional gas reservoirs and unconventional gas accumulations; and (4) both are clustered lithologic gas accumulations on a large scale. The differences are: (1) different source-reservoir-seal assemblages give birth to two kinds of accumulations, i.e. extensive accumulations and large-scale patchy accumulations; (2) different source kitchen continuity and gas supply potentials lead to different enriched gas-bearing layer series and different abundances. Timely understanding of the similarities and differences between large-scale natural gas accumulations with low porosity and permeability in these two basins are conducive to avoid risks and improve exploration success ratio and benefits.

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Trend and progress in global oil and gas exploration

Hu Wenrui; Bao Jingwei and Hu Bin

. 2013, 40(4): 2-0.

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Major progress achieved in oil and gas exploration in terms of reserves, number of oil and gas fields and discovery of large oilfields were analyzed, trend and progress of global oil and gas exploration in eight aspects were elaborated, and four enlightenments for oil and gas exploration in China were proposed. The following aspects have become the shifting trend of oil and gas exploration around the world: from oil and gas reservoirs to source rocks, from trap to large area reservoir, from structural reservoirs and lithological reservoirs to unconventional continuous reservoirs, from structural highs to low sags and slopes, from conventional hydrocarbon to unconventional hydrocarbon, from middle depth layers to deep and ultra-deep layers, from shallow and middle depth sea to deep and ultra-deep sea, and from conventional zones to extreme zones. China should put more effort into the research on basic exploration theory and key techniques, attach more attention to the role of exploration engineering technology, seek the effective way for comprehensive exploration of oil and gas resources, and strengthen secondary exploration of old oil and gas fields. The major transformation in oil and gas exploration field and strategy will be beneficial to the discovery of more oil and gas fields in China.

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Simulation of petroleum exploration based on a conceptual decision model: Taking the Dezful Embayment in southwestern Iran as an example

Soleimani M

. 2013, 40(4): 2-0.

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A conceptual decision model was designed to approximate the exploration of a petroleum basin in the Dezful Embayment, southwestern Iran. The model consists of four parts, namely, attribute creation, exploration simulation, decision analysis, and economic evaluation, and it is used to make exploration decisions according to Bayesian decision theory. With the oil and gas exploration in the Dezful Embayment as an example, the responses of oilfield geologic conditions to various exploration methods were obtained to create abnormal areas and reservoir distribution, and to simulate the exploration process of the basin. The simulation results prove that the model is accurate. The reservoirs in the study area are controlled by structural elements, so seismic data rather than surface and subsurface geologic maps should be used to figure out reservoir scale and targets.

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Geological concepts, characteristics, resource potential and key techniques of unconventional hydrocarbon: On unconventional petroleum geology

Zou Caineng; Zhang Guosheng; Yang Zhi; Tao Shizhen; Hou Lianhua; Zhu Rukai; Yuan Xuanjun; Ran Qiquan; Li Denghua and Wang Zhiping

. 2013, 40(4): 2-0.

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Petroleum geology is developing in two directions: conventional petroleum geology and unconventional petroleum geology. Conventional petroleum focuses on “whether hydrocarbon is accumulated in traps”, and intensively studies six geological elements, i.e. source rock, reservoir, cap rock, migration, trap, and preservation, and their coupling relationship. Unconventional petroleum geology focuses on “whether hydrocarbon is continuously accumulated in reservoirs”, and intensively studies six geological properties, i.e. lithology, reservoir quality, brittleness, petroliferous properties, source rock properties and stress anisotropy, and their coupling relationship. In this article, hydrocarbon accumulation model and theoretical equation in different pore-throats diameters, “L-type” production curve and theoretical prediction model for unconventional hydrocarbons, are proposed to uncover the unconventional hydrocarbon formation mechanism and development rule. This article defines the basic concept and geological characteristics, analyses the resource potential, and proposes the exploration and exploitation core technology of unconventional hydrocarbon. Unconventional hydrocarbon is characterized by the following two key marks: (1) continuous distribution of hydrocarbon-bearing reservoir bodies, and no obvious trap boundary, and (2) no naturally stable industrial production, and no obvious Darcy percolation. Based on systematical research, the proportion of global unconventional and conventional hydrocarbon resources is 8︰2, in which the unconventional oil is almost equal to conventional oil, and the unconventional gas is about 8 times conventional gas. In China, the potential of unconventional hydrocarbon resource is very huge, as unconventional oil is about 240×108 t and unconventional gas is about 100×1012 m3. The exploration and exploitation of different types of unconventional hydrocarbon should be done progressively. In recent years, tight gas and tight oil need to realize industrial reserves and productions, and meantime more shale gas industrial pilot areas should be constructed, and shale oil should be quested. In future, an unconventional hydrocarbon industrial system, which will include unconventional petroleum geology, fine-grains sedimentology, unconventional reservoir geology six geological properties prediction geophysics, large-scale horizontal drilling & fracturing, “factory-like” operation pattern, low cost management & policy subsidy, and talents training, is urgently needed to be established.

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Geological modeling of excellent fractured-vuggy carbonate reservoirs: A case study of the Ordovician in the northern slope of Tazhong palaeouplift and the southern area of Tabei slope, Tarim Basin

Ni Xinfeng; Shen Anjiang; Pan Wenqing; Zhang Ronghu; Yu Hongfeng; Dong Yong; Zhu Yongfeng and Wang Chaofeng

. 2013, 40(4): 2-0.

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Based on the reservoir characteristics of individual wells, the combined main controlling factor of fractured-vuggy reservoir and reservoir space synthesized modeling was adopted to establish geologic models for the Ordovician reservoirs in the northern slope of the Tazhong palaeouplift and the southern area of the Tabei slope. Geologic models for six types of wells were established: (1) sequence boundary controlled cave + fracture-vug; (2) cave + fracture-vug on the top of cave controlled by fractures; (3) cave in the surface layer + fracture-vug under the cave controlled by the sequence boundary and faults; (4) single fracture-vug controlled by the sequence boundary and faults; (5) single vug controlled by deep hydrothermal fluids along faults and fractures; (6) single fracture controlled by faults and fractures. Two types of synthesized geologic models were established under the tectonic background of cuesta, namely, platform type slope of the Tazhong area and the gentle slope of the Tabei area. Type 1 and 2 reservoirs are common in the Yijianfang-Yingshan Formation of the HA6-Xinken Region, and type 3 and 5 reservoirs are common in the Yingshan Formation of the ZG8-ZG43 Region. A comprehensive evaluation shows that the reservoir of cave + fracture-vug on the top of cave controlled by the sequence boundary is the best, followed by cave + fracture-vug on the top of cave controlled by faults. So the areas that meet configuration of caves and fracture-vugs and single vug controlled by deep hydrothermal fluids along faults and fractures are important targets for exploration and development.

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Geological characteristics and resource potential of lacustrine shale gas in the Sichuan Basin, SW China

Li Yanjun; Feng Yuanyuan; Liu Huan; Zhang Liehui and Zhao Shengxian

. 2013, 40(4): 2-0.

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The geochemical characteristics of shale such as total organic content, type and maturity, shale sedimentary environment, geological characteristics, and scale of development were analyzed to study the geological characteristics and resource potential of lacustrine shale in the Lower Jurassic Ziliujing Formation in the Sichuan Basin. The Lower Jurassic Ziliujing Formation lacustrine shale is mainly developed in the Dongyuemiao and Da’anzhai members. The geochemical analysis of the organic carbon content, kerogen macerals, biomarker compounds and vitrinite reflectance of the shale samples showed that the total organic content is generally over 1.0%; the main organic type is II1-III, but type II1 is in the central part of the basin; the vitrinite reflectance value (Ro) is 1.05%-1.82%, thus the shale has a strong ability to generate gas. The thickness of the distributed Ziliujing shale is approximately 40-150 m, the average porosity is 1%-5%, and the permeability is 0.001×10-3-0.100×10-3 μm2. The lacustrine shale consists of different assemblages: pure shale, shale with imbedded lime band, and shale with thin-middle shell limestone. The shale has high quartz content, favorable for exploitation of shale gas; the lime band and the shelly limestone, which are developed in the shale can further improve the shale economic recoverability. The estimated shale gas resources of the Ziliujing lacustrine shale by volumetric method is about 3.8×1012- 8.7×1012 m3.

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Accumulation mechanism of the Yingdong I field in the Qaidam Basin, NW China

Sun Ping; Guo Zeqing; Liu Weihong; Zhang Lin; Tian Jixian; Zhang Shaosheng and Zeng xu

. 2013, 40(4): 2-0.

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The Yingdong I field is a large oil and gas field of shallow burial depth, high yield and high abundance. Its accumulation model is established by the analysis of the fault opening and sealing mechanisms. Faults in the field have the characteristics of sealing in shallow formations and opening in deep formations. Shallow faults are sealed because shallow formations were still in the stage of weak diagenesis, and under the influence of diagenesis, shale smear was formed in mudstones which were elongated and uninterrupted, and cataclasis happened in sandstones. On the other hand, deep faults are open because it was difficult for shale smear to form as mudstones in the fault zone had experienced so intense diagenesis that brittle fractures were produced and considerable cracks were formed. The accumulation model can be summarized as follows: deep faults transporting, shallow faults sealing, lower-generation and upper storage and late accumulation, that is to say, when oil and gas migrated along the deep opening faults upward from the source rock, the reservoirs were formed in the shallow layers because of faults sealing. The Shizigou-Youshasha, Kaitemilike,Yanshan and Youdunzi structures have a shallow structure style and accumulation model similar to that of the Yingdong I and are the favorable zones for exploration

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Effects of base-level cycle on mouth bar reservoir micro-heterogeneity: A case study of Es2-9 member of Shahejie Formation mouth bar reservoirs in Shengtuo Oilfield

Liang Hongwei; Wu Shenghe; Wang Jun; Yue Dali; Li Yupeng; Yin Senlin; Yu Chen and Wang Xiabin

. 2013, 40(4): 2-0.

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To identify the factors and mechanisms affecting reservoir micro-heterogeneity in the same type of microfacies at different stages of cycle, the main controlling factors of the reservoir micro-heterogeneity of the mouth bar in Es2-9 Formation of the Shengtuo Oilfield were analyzed based on the sedimentary dynamic analysis of high resolution stratigraphic sequence and quantitative parameters of reservoir micro-heterogeneity. The base level cycles of different stages have a differential control on the reservoir micro-heterogeneity of the mouth bar. The changes of the base level in different orders lead to variation in accommodation space and sediment supply, and in turn changes in sedimentary environments of mouth bar at different stages, as a result, the reservoir micro-heterogeneity of the single mouth bar in short-term base level cycle is strong at bottom and weak at top, the reservoir micro-heterogeneity of compound mouth bar (formed by different stages of single mouth bar) in middle-term base level cycle gets weaker from bottom-up, and the reservoir micro-heterogeneity of compound mouth bar at different stages of long-term base level cycle has no obvious pattern.

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Influences of feldspars on the storage and permeability conditions in tight oil reservoirs：A case study of Chang-6 oil layer group, Ordos Basin

Xu Lei; Shi Yongmin; Xu Changsheng; Yang Yue; Li Hong and Chai Zhi

. 2013, 40(4): 2-0.

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Based on rock thin slice observation, casting thin slice identification, high-pressure mercury injection, constant velocity mercury injection, and X-ray diffraction, influences of feldspar minerals on the storage and permeability conditions in Chang-6 oil layer group in the Yanchang Formation of the Ordos Basin were studied from crystallography and mineralogy perspective through high resolution field emission CMOS scanning election microscope observation and analysis. Due to the differences of crystal structure and chemical composition, the brittleness and solubility of feldspar minerals varied greatly. The results indicate that basic plagioclase such as anorthite tends to split along the cleavage to form the new flow channel in the formation conditions. Alkaline feldspar rich in potassium such as K-feldspar tend to corrode along the cleavage to form secondary porosity. The brittleness and solubility of acid plagioclase, such as albite, are between anorthite and K-feldspar. The main pore type in Chang-6 oil layer group of Ordos Basin is residual inter-granular pore, the secondary pores generated by corrosion and fracture of feldspar have little contribution to porosity. In the area with higher content of anorthite, the micro-crack resulted from breaking in cleavage effectively improve the permeability. The contribution of feldspar minerals to permeability is ranked from great to small as anorthite, orthoclase and albite.

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Assessment on petrophysical parameters of clastics using well logs: Taking the Upper Miocene in El-Wastani gas field, onshore Nile Delta, Egypt for example

Ezz S El-Din; Maher A Mesbah; Mohamed A Kassab; Ibtehal F Mohamed; Burns A Cheadle and Mostafa A Teama

. 2013, 40(4): 2-0.

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Based on logs of ten wells in the El-Wastani gas field, onshore Nile Delta, Egypt, petrophysical evaluation for the Upper-Miocene Qawasim Formation and Abu Madi Formation in the El-Wastani gas field was accomplished. The lithology of these formations was analyzed using cross plots of logging parameters, and petrophysical parameters including shale volume, porosity, water saturation and hydrocarbon pore volume were assessed. The Neutron/Density, Neutron/Gamma-ray and Litho-saturation cross plots of the wells show that the main lithology of the Lower Abu Madi unit is sandstone with shale intercalations, while the lithology of the Qawasim Formation is mainly composed of shale with sandstone intercalations. The cut-offs of shale volume, porosity and water saturation for productive hydrocarbon pay zones are 50%, 10% and 70%, respectively, which were got based on cross-plots and Gamma-ray log data. Contour maps for parameters such as net pay thickness, average porosity, shale volume and water saturation were prepared and it is found out that the Abu Madi Formation and Qawasim Formation in the study area have promising reservoir characteristics; A prospective region for gas accumulation trends northwest-southeast in the study area, especially favorable in the central part.

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Block compressed storage and computation in large-scale reservoir simulation

Wang Baohua; Wu Shuhong; Han Dakuang; Huan Guanren; Li Qiaoyun; Li Xiaobo; Li Hua and Zhou Jiuning

. 2013, 40(4): 2-0.

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The block compressed storage and solving methods in reservoir simulation are explored to resolve large sparse linear equations emerging in three-phase black oil model. In this paper, the active nodes are compressed firstly, and then the block main diagonal elements, nonzero block elements in lower triangular and upper triangular are separately stored into three real arrays. Owing to the coefficient matrix arising in the reservoir simulation being symmetrical, the addresses of block elements in lower triangular are deposited in three integer arrays. This block compressed storage method can save lots of memory and reduce the search frequencies of non-zero elements. On the basis of such compression storage, the block incomplete LU preconditioned generalized minimal residual method (GMRES) is adopted to solve the equations, showing that it is an effective method possessing fast convergence and good stability. Testing of black oil model example reveals that the block compressed storage and solving methods are effective in solving the large-scale reservoir simulation.

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A water breakthrough warning system of high-yield wells in fractured-vuggy reservoirs in Tahe Oilfield

Luo Juan; Lu Xinbian; Wu Bo; He Xinming; Li Xinhua and Wang Lei

. 2013, 40(4): 2-0.

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A water-out warning system is set up by using water breakthrough data of high yield wells, summing up warning parameters of water-out, and combining with influencing factors of water-out. During the development of Ordovician karst-cave and fracture-vug reservoirs in the Tahe Oilfield, bottom water goes through four stages: prior water invasion, cone period, supporting cone period and breakthrough period. In the late period of the supporting cone, bottom water leads to pressure oscillation in the dissolved cave system, which affects the bottom-hole pressure to some extent. According to the nodal analysis theory, the change of bottom-hole pressure will lead to changes of wellhead pressure, and abnormal signals such as abnormal bottom-hole flowing pressure, tubing pressure, casing pressure, or output. According to geological, engineering, production management factors, and abnormal signals before water-out, 31 indices for water-out risk evaluation are summed up, and early water breakthrough warning technique for high-yield wells is established. Application of the technique to 146 no-water high-yield wells shows the warning technique works well and extends the water free production period.

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Mechanism and gelling effects of linked polymer solution in the core

Liu Jinxiang; Lu Xiangguo; Liu Jingfa; Hu Shuqiong and Xue Baoqing

. 2013, 40(4): 2-0.

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By using Bush viscometer, dynamic and static laser scatter instrument, scanning electron microscope and core flow experimental apparatus, experiments were conducted to study the viscosity, molecular coil dimensions, molecular configuration and static gelation of amphoteric polymer solution and linked amphoteric polymer solution in porous media and affecting factors, and to analyze the gelation mechanism of linked polymer solution in the core. The results showed that with the increase of solvent water salinity, the cross-linking reaction rate increases; with increase of aging time, the gelling effect gets stronger and stable; with the increase of shear time, the lineation of polymer molecules gets more obvious, the gelling effect in pores gets worse; under the condition of low permeability, the cross-linking reaction mainly is intramolecule cross-linking; with the increase of core permeability, i.e. the increase of pore size, the gelling effect gets better in the core, and inter-molecular cross linking reaction is more likely to take place. The experimental data and theoretical analysis showed that in the linked amphoteric polymer solution, the cross-linking reaction occurs between the different branched-chain of the same molecule firstly (intra-molecular cross-linking), then the cross-linking reaction extends to different polymer molecules (i.e. inter-molecular cross-linking).

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Impact of temperature on the isothermal adsorption/desorption characteristics of shale gas

Guo Wei; Xiong Wei; Gao Shusheng; Hu Zhiming; Liu Honglin and Yu Rongze

. 2013, 40(4): 2-0.

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Isothermal adsorption and desorption experiments under different temperatures were carried out with the Longmaxi Formation shale samples collected from southern Sichuan. The experimental results show that temperature affects the adsorption and desorption capacity of shale, the adsorption capacity of shale decreases with temperature increase. The adsorption curve and desorption curve of shale are not coincident and the thermodynamic reason for the hysteresis of the desorption curve is that the isosteric heat of the shale adsorption process is greater than that of the desorption process. The Langmuir model and desorption model can describe the isothermal adsorption and desorption processes very well, respectively. Isothermal adsorption and desorption curves under different temperatures can be predicted by isosteric heat curves which match the experimental results. Shale gas production is a process of gas desorption and the desorption characteristics directly impact the production of shale gas, so the desorption model should be taken into consideration in the shale gas production forecast and numerical simulation.

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Experiments of vertical fracture propagation based on the digital speckle technology

Liu He; Wang Suling; Jiang Minzheng and Zhang Yiming

. 2013, 40(4): 2-0.

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The vertical crack propagation behavior for sandstone/mudstone layered specimen made by the similar material was analyzed. The stress and strain field was obtained using Digital Speckle Correlation Method to analyze the propagation characteristics of vertical cracks. The test shows that the higher the strength of the interface layer, the more susceptible the crack deflects from the side of the low-strength than from the side of the high-strength of the material. It is easy for the interface to unglue when the interfacial adhesion strength is weak, which results in the dislocation propagation after the crack passing the interface. The longer the growth path is before the crack passing the interface, the more likely it deflects after passing the interface. Similarly, the shorter the initial prefabricated crack is, the more susceptible it deflects after the crack passing the interface. The main factor of the deflection is the difference in the properties of the composite materials, resulting in a larger shear strain of the interfacial layer. The shear strain can induce type Ⅱ shear fracture, so it is the main factor leading to crack deflection. The bigger the shear deformation is, the more intensive the crack deflection is.

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Numerical analysis and verification of pile penetration into stiff-over-soft clay

Zhang Jian; Tang Wenxian; Su Shijie; Qin Wenlong; Wang Jingfang and Liu Renchang

. 2013, 40(4): 2-0.

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A numerical model for jack-up penetration process was built based on the geotechnical centrifugal model test by Hossain M S. The soil flow mechanism and the relationship between penetration depth and penetration resistance were analyzed based on numerical results. The distribution pattern of the spudcan bottom pressure was investigated for the first time. The numerical results are in good agreement with Hossain M S experimental results, which indicates that the proposed model is reliable. The numerical results show that, soil flow failures, such as surface and interface swelling, cavity formation, and soil backflow, happen in the penetration process; the lower the strength ratio between stiff and soft clay is, the smaller the volume of stiff block under the spudcan is, the more continuous and uniform the stiff clay distribution above the spudcan is, and the deeper the cavity is. The higher the soil unit weight, the more the backflow stiff soil above the spudcan and the shallower the cavity. The soil unit weight has almost no effect on the stiff soil shape and volume under spudcan. The higher the strength ratio between stiff and soft clay or the lower the soil unit weight is, the more likely the punch-through occurrs. The bottom pressure first increase, then decrease, and increase sharply, from inside to outside, which proves that the linear assumption of the spudcan bottom pressure in ‘Rules for Mobile Offshore Drilling Units’ does not conform to the fact.

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A biomimetic drilling fluid for wellbore strengthening

Xuan Yang; Jiang Guancheng; Li Yingying; Geng Haonan and Wang Jinshu

. 2013, 40(4): 2-0.

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Based on biomimetic technology, wellbore strengthener GBFS-1 and shale inhibitor YZFS-1 were synthesized imitating the mussel protein which has super adhesion. A new drilling fluid system centering on the two biomimetic agents was designed and prepared in order to enhance the strength of shale rocks near wellbore and maintain wellbore stability. Various inhibition evaluation tests show that YZFS-1 can strongly inhibit clay hydrated swelling and the resulting shale dispersion, due to the adsorption and self-polymerization of YZFS-1 molecules in the interlayer of clay. Besides the ability of controlling fluid loss, GBFS-1 can also adhere to shale rock, produce dense and water impermeable biomimetic shell that has relative strong cohesion strength after spontaneous cure. The shear strength tests show that the shear strength of two shale pieces glued together by the biomimetic shell in aqueous environment is obviously stronger than glued by several commonly-used binders. Through compatibility evaluation and dosage optimization of the additives, the formula of biomimetic drilling fluid was established, and its performance was evaluated and compared with another anti-caving drilling fluid. The results show the biomimetic drilling fluid is better in all basic performances than the anti-caving drilling fluid on the whole, and can effectively inhibit shale swelling and dispersion.

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Seismic technology for predicting highly profitable wells in the fractured-vuggy carbonate reservoirs

Yang Ping; Sun Zandong; Liang Xianghao; Li Haiyin and Dan Guangjian

. 2013, 40(4): 2-0.

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Aiming at the problems of “high but unstable production” and low success ratio in highly profitable well prediction of the Ordovician fractured-vuggy carbonate reservoirs of the Tarim Basin, based on their features of small size, huge burial depth and high heterogeneity, and proceeding from the similar bead-like reflections, this study tries to find out and quantify the differences in oil and gas bearing scale between the reservoir units, and accurately works out the reserves in them. An integrated seismic technical strategy was proposed which bases on full-azimuth and high-density acquisition, centers on amplitude-preserved prestack depth migration, and stresses on the quantitative reservoir description. By figuring out the storage spaces of the fractured-vuggy reservoirs, the connection conditions between fracture-cave bodies, and the hydrocarbon bearing conditions of the fracture-cave bodies, the fracture-cave units which have larger reserves are chosen as drilling targets. The application results in Well Ha 7 area of the Tabei region proved that the fracture-cave bodies can be precisely studied and the fracture-cave units can be accurately delineated by these techniques, and the success ratio of the highly-profitable well prediction can be raised accordingly.

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Estimation of in-situ mechanical properties of gas hydrate-bearing sediments by well logging

Ning Fulong; Wu Nengyou; Li Shi; Zhang Ke; Yu Yibing; Liu Li; Sun Jiaxin; Jiang Guosheng; Sun Changyu and Chen Guangjin

. 2013, 40(4): 2-0.

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Taking Well SH7 in South China Sea and Well Mount Elbert in Alaska North Slope permafrost as examples, mechanical properties of gas-hydrate-bearing sediments (GHBS) in ocean and permafrost were estimated based on the method used in conventional oil and gas reservoirs with log data, and the results were compared with other tests or calculations. The correlations between mechanical parameters and log velocities in conventional oil and gas industry can obtain reasonable strength parameters of oceanic GHBS, such as cohesion, internal frictional angle, tensile strength and shear strength. However, the estimations of shale content of oceanic GHBS, internal frictional angle of permafrost GHBS, elastic parameters such as Young’s modulus and bulk modulus of oceanic and permafrost GHBS have big errors. In the future, more efforts should be given to build suitable relations between mechanical parameters and velocities or more accurate correlations between mechanical parameters and hydrate saturation. Thus, with the aid of velocities and hydrate saturations from well logging, the mechanical properties of GHBS can be more accurately evaluated.

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, Volume 40 Issue 4