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01 January 2019, Volume 39 Issue 6 Previous Issue    Next Issue

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High-Yield Reservoir Prediction in Jurassic Channel Sandstones of Fudong Slope Area, Junggar Basin HE Kaiquan, ZHOU Liping, DENG Yong, LIU Xiaohu, LIU Yahui, WU Xiaoning 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180601 Abstract ( 180 )   PDF (4396KB) ( 413 )   Save The Jurassic Shishugou group in Fudong slope area of Junggar basin is characterized by the development of channel-type sandbodies, which has the characteristics of “fault connected with oil source & reservoir controlled by lithology”. The production varies greatly among different sandbodies and it is difficult to predict high-yield reservoirs with conventional techniques and methods. On the basis of newly acquired “high density, wide azimuth and broadband” 3D seismic data of Wellblock Fudong-5, this paper analyzes the seismic response characteristics of channel sandstones. Firstly, the pre-stack AVO derivative attributes are used to distinguish oil and water in channel sandstones and the reservoirs are identified qualitatively; secondly, the effective porosity and permeability obtained from NMR logging are used to calculate porosity and permeability parameters comprehensively, and the correlation with the reservoir production is established; then the low-yield, medium-yield and high-yield oil layers can be distinguished in the reservoir by the geostatistical inversion and the production can be predicted quantitatively. Finally, the prediction results of high-yield reservoir can be obtained. The matching technology for predicting high-yield reservoirs of Jurassic channel sandstones in Fudong slope area has been integrated and formed, which can effectively guide the deployment of high-yield wells in the later period of the study area Related Articles | Metrics

Seismic Response Characteristics of Fractured-Vuggy Reservoirs in Deep Carbonate Horizons of Tarim Basin SUN Dong1, YANG Lisha1, CHEN Juan1, ZHANG Huquan1, PAN Wenqing2, DAI Dongdong1 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180602 Abstract ( 177 )   PDF (12502KB) ( 94 )   Save Taking the Palaeozoic carbonate fractured-vuggy reservoir in Tarim basin as an example and with the forward modeling of elastic-wave wave equation, seismic response characteristics of every type of carbonate reservoirs based on the influence factors on development of the reservoirs relevant with reef-shoal, weathering crust and fault are discussed. It is concluded that the seismic reflection of the reef-shoal reservoir is characterized by mound-shaped and sheet-like reflections on palaeo-geomorphologic structural highs, weak reflection, chaotic reflection and strong bead-like reflections, etc.; while the weathering crust karst reservoir is characterized by sheet-like seismic reflection in the top boundary, sheet-like seismic reflection along horizons, weak-strong bead-like reflection and weak reflection; and the fault-related karst reservoir is dominated by longitudinal long bead-like and multiple bead-like reflections, complexes of sheet-like, bead-like and chaotic reflections, and bead-like reflection at the intersections of faults, etc. Analysis on seismic response characteristics of carbonate reservoirs from the view of reservoir controlling factors is a feasible method, which could provide references for reservoir prediction method selection, exploration potential analysis and target optimization Related Articles | Metrics

Depositional Environment of Coal and Oil Shale of Middle Jurassic Shimengou Formation in Tuanyushan Area, Qaidam Basin CHEN Lingling1,2, MENG Qingtao1,2, LIU Zhaojun1,2, XU Yinbo3, SUN Pingchang1,2, WANG Kebing1,2 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180603 Abstract ( 126 )   PDF (2632KB) ( 323 )   Save The Middle Jurassic coal and oil shale are widely developed in the Tuanyushan area in the northern margin of the Qaidam basin, but the exploration level in the area is relatively low and the researches on the depositional environment and genesis of the coal and oil shale are relatively weak. Therefore, the paper uses the QD-2 full cored well in Tuanyushan area to study the organic geochemical characteristics and depositional environments of the coal and oil shale in the study area based on the analysis on rock pyrolysis, total organic carbon, industrial quality parameter, gas chromatography and gas chromatography-mass spectrum. The study shows that the oil shale is characterized by high ash content, low organic carbon content and low-medium oil-bearing rate, and the coal belongs to low ash content, high organic carbon content and low metamorphic grade lignite. N-alkanes, isoprenoid, terpenoid, steroid and aromatic hydrocarbons are detected in the coal and oil shale. On the gas chromatography, N-alkanes in both coal and oil shale are in single-peak distributions with the first lower and later higher shape. The Pr/Ph value of coal is higher than that of oil shale, the relative content of the regular sterane is C29>>C28>C27, abundant sesquiterpenoids and diterpenoids are detected in aromatic compounds. The comprehensive analysis shows that the coal and oil shale are at the immature stage of evolution and the organic matter mainly comes from terrestrial gymnosperms. The oil shale formed in a weak oxidation, fresh water and shallow lake environment and the coal formed in an oxidizing marsh environment. Therefore, as for the source of organic matters, there are no significant differences between the coal and oil shale, but their sedimentary environments are largely different. The comparison shows that the differences existed in the organic matter type, source and sedimentary environment result in the different occurrence characteristics of the oil shales in the coal-bearing intervals and in the shale intervals in the Shimengou formation of Tuanyushan area in Qaidam basin Related Articles | Metrics

Comparison Between Two Types of Slope-Break Belts in Pearl River Mouth Basin ZHANG Shangfeng1a,1b, CAO Yuanting2, ZHANG Changmin1a, SHI Hesheng3, WANG Yaning1a, YIN Yanshu1a, ZHU Rui1a 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180604 Abstract ( 136 )   PDF (6231KB) ( 423 )   Save Slope-break belt is the basis of sequence stratigraphic classification and correlation, stratigraphic architectural analysis and sequence model establishment. A lot of researches have been done on different types of slope breaks, however, most of them focused on the analysis of a single slope-break belt. The stratigraphic sequence analysis of the Pearl River Mouth basin in the northern South China Sea shows that there are double slope breaks since the Neogene in the basin, that is, the sedimentary slope-break belt of the continental shelf and the geomorphic slope-break belt of the shelf edge exist simultaneously, and the controls of different slope-break belts on sedimentary sequence are various. Based on the comparison between the two types of slope-break belts from the aspects of formation background, development and evolution, topography and geomorphology characteristics, and sedimentary systems, it is believed that the formation of the geomorphic slope-break belt is closely related to the tectonic action, as a result, three types of stratigraphic sequences are formed including four partitioned, three partitioned and two partitioned system tracts, respectively. The formation of sedimentary slopes is obviously controlled by paleogeomorphology, sediment supply process and non-equilibrium unloading, and the last two types of stratigraphic sequences are dominant Related Articles | Metrics

Simulation Experiment of Feldspar Supergene Leaching and Dissolution FENG Jiarui1, GAO Zhiyong1, CUI Jinggang1, FAN Xiaorong2 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180605 Abstract ( 179 )   PDF (3506KB) ( 194 )   Save Using the self-developed diagenetic simulation system, the paper selects the medium-sized feldspar sandstone as the research object, and carries out diagenetic simulations on microscopic dissolution characteristics, soluble components, ion changes of diagenetic fluids and dissolution products of feldspar dissolution. The study shows that under the condition of acidic fluid, different types of feldspar have different degrees of dissolution and intense dissolution occurs to plagioclase, and its particle surface shows a harbor-shaped deep groove or dissolutions along the direction of the twin crystals. Dissolution mostly occurs at the edge or in the interior of the particles of potassium feldspar. The variations of the concentrations of K+, Na+, Ca2+, Mg2+, Al3+, Si4+ etc. reflect the status of feldspar dissolution, and the increase of the concentrations of K+, Na+ and Ca2+ indicate the acceleration of the dissolution rate of K-feldspar, albite and plagioclase. The concentration of K+ during the feldspar dissolution is relatively low and the ion is easy to be taken away rapidly, which result in the difficulties of K+ concentration required by illite deposition to be reached. Therefore, the authigenic clay minerals generated during the feldspar dissolution are mostly kaolinite. The changes of Mg2+ concentration may represent the dissolutions of carbonate and clay minerals at the late stage. Flow rate of acid fluid, temperature, surface area of feldspar grain and dissolution time are the key factors influencing feldspar dissolution Related Articles | Metrics

Base Rock Weathering Crusts and Petroleum Accumulation in Dongping AreaQaidam Basin WU Jin1, GAO Xianzhi2, ZHOU Wei3, ZHANG Yongshu4, YANG Yun4, YOU Chao4 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180606 Abstract ( 183 )   PDF (3952KB) ( 467 )   Save The Dongping area is located in the piedmont slope of the Altun Mountains in Qaidam basin and far from the hydrocarbon center. Two gas reservoirs have been discovered in the base rocks of Dongping-1 block and Dongping-3 block, respectively. The forming of the gas reservoirs in the base rocks of the Dongping area are closely related to the base rock weathering crust. On the basis of the study on the features of mineral alteration, weathering products and dissolved pore development, the structure of the base rock weathering crust in the area is classified into completely weathered layer, semi-weathered layer and unweathered layer, the semi-weathered layer is further divided into weathering dissolved belt and weathering disintegration belt and the two belts have different dissolution and mineral alteration degree. Dissolved pores and strong-dissolved widened map crackings are developed in the weathering dissolved belt, and weak-dissolved low-angle weathering joint fissures and high-angle structural fractures are found in the weathering disintegration belt. The average thickness of the base rock weathering crust in individual wells is more than 200 m in the Dongping area, much larger than that in Kunbei area, which is related to the paleo-terrain of the area before the deposition of the Paleogene. Because granitic gneiss is easier to be weathered than granite, the weathering crust in Dongping-1 block(where granitic gneiss is mainly distributed) is thicker than that in Dongping-3 block (where granite is mainly distributed). Additionally, the weathering crust is thick in the area where fault and fracture are developed. The semi-weathered layer plays an important role in oil and gas migration from hydrocarbon generation sag to the study area, meanwhile, it is the key reservoir for hydrocarbon accumulation in base rocks. The completely weathered layer is relatively thin and can’t be a good cap rock, so it only can act as a barrier or an interlayer Related Articles | Metrics

Geochemical Characteristics of C5~C7 Light Hydrocarbons in Natural Gas of Southwestern Qaidam Basin CHEN Kefei1,2,3, ZHOU Shixin1,2, LI Jing1,2, ZHANG Chen1,2,3, ZHANG Yuhong1,2,3, LI Yuanju1,2,3, MA Yu1,2,3 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180607 Abstract ( 148 )   PDF (1391KB) ( 309 )   Save Focusing on the C5~C7 light hydrocarbons in natural gas, combined with natural gas components and carbon isotopes, the paper studies the organic precursor type and maturity, hydrocarbon generation temperature and secondary hydrocarbon reconstruction in Yingdong, Wunan and Zhahaquan oilfields in southwestern Qaidam basin. The results show that the C7 compounds in the natural gas of the 3 oilfields exhibit high n-heptane contents and the C7 compounds in Wunan oilfield have relatively high methylcyclohexane content. Based on the carbon isotope analysis, it is considered that the natural gas from Yingdong, Wunan and Zhahaquan oilfields mainly belong to oil-type gas, and coal-type gas and mixed gas are found in Wunan and Zhahaquan oilfields. The heptane and isoheptane values indicate that the natural gas are mostly in the mature-highly mature stage, based on the δ13C1-Ro% relationships, the calculated natural gas maturity is 0.8%~1.5% with the average value of 1.2%, indicating these gases were mainly generated in the mature stage. The calculated natural gas generation temperatures can roughly reflect petroleum forming temperatures of the main part of the modern reservoir. The petroleum generation temperatures in Yingdong, Wunan and Zhahaquan oilfields (124~129 ℃) are higher than those in Qigequan and Shizigou oilfields (108~109 ℃), showing that the natural gas maturity in Yingdong, Wunan and Zhahaquan oilfields are even higher. Through light hydrocarbon analysis, several oil and gas reservoirs suffered from biodegradation, evaporative fractionation and water washing have been identified Related Articles | Metrics

Reservoir Architecture and 3D Geologic Model of Alluvial Fan: A Case Study of Wellblock Hong-18 of Hongche Area, Junggar Basin CHEN Juan1a, WU Xiaojun2, CHEN Yanhui2, YIN Senlin1b 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180608 Abstract ( 237 )   PDF (3829KB) ( 433 )   Save Regarding the complicated sedimentary system of alluvial fans located in the margin of Junggar basin, with the data of well patterns and outcrops and using the method of hierarchical bounding surface analysis, the paper performs a leveled dissection on the internal architecture of alluvial fan reservoirs and establishes the reservoir architecture patterns and 3D geologic models for alluvial fans of the lower Karamay formation in the Wellblock Hong-18 of the northwestern margin of the basin. The 4-order architecture of the alluvial-fan sedimentary system is made up of trench-flow sandy conglomerate, laminar-flow gravel, high-energy channel sandbody, low-energy channel sandbody and runoff channel sandbody, meanwhile, it includes some low-quality reservoirs such as flood sandbody, sheet-flood sandbody and fine-grained flood deposit. The internal architectures of different facies belts in the alluvial fans are different. Trench flow-laminar flow facies belts are dominated by connected sheet sandy conglomerate which is the product of the superimposition of complicated sandy conglomerate and a single sandy conglomerate body is 1.2~1.6 km wide; the braided-flow facies belt is the complex superposition of the high-energy channel sandbody, low-energy channel sandbody and sheet-flood sandbody, among which the high-energy channel is 400~600 m wide and the low-energy channel is 100~250 m wide; the runoff channel belt is distributed in the fine overbank deposits in the shape of mosaics and shows an isolated narrow strip shape, and the width of a single runoff channel ranges from 50 m to 80 m. Based on the detailed geological research, the paper establishes 3D architecture models for the study area by using deterministic modeling combined with artificial interactive methods Related Articles | Metrics

Influences of Gelled Acid on Mechanical Properties of the Ordovician Carbonate Rocks in Block Shunbei, Tahe Oilfield LI Chunyue1, WANG Yang1, DENG Peng1,2, GUO Yintong2, XU Feng3, ZHOU Jun2 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180609 Abstract ( 148 )   PDF (2211KB) ( 278 )   Save From the perspective of macroscopic and microscopic points, the paper studies the influences of gelled acid used during fracturing on the mechanical properties of the Ordovician carbonate rocks in the Block Shunbei of Tahe oilfield, which could provide basis for efficient development of the carbonate reservoirs in the target blocks. The experiments were carried out to test the influences on microscopic structures and its mechanical properties of carbonate rock samples after treatment by gelled acid and the results showed that the mineral components of the Ordovician carbonate rocks in Shunbei area are characterized by high contents of carbonate minerals, low content of quartz and a few impurities; after the static acid-rock reaction, the intercrystal distance of minerals significantly increases and the calcite content reduces from 93% to 88%, indicating a high-brittleness fracturable reservoir; the static acid-rock reactions in different acid fluids and the corresponding uniaxial compression tests show that the optimal reaction time is 30 minutes, and each physical parameter and mechanics index get worse obviously; the density and P-wave velocity decrease obviously after 30 minutes of gelled acid treatment for the rock samples and the tensile and shear strengths significantly drop; the gelled acid as a reaction acid fluid can result in acid etching to the macrostructures and some damages to micropores of the carbonate rock samples. Therefore, the gelled acid is of great significance for carbonate reservoir fracturing and fracture propagation Related Articles | Metrics

Evolution of Rocks and Crude Oil in Resevoirs During Fire Flooding SHI Yaoli, LYU Shiyao, SHI Xiaorong, YANG Zhi, CHEN Feng, YANG Fengxiang 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180610 Abstract ( 139 )   PDF (3836KB) ( 540 )   Save Temperature is the main factor influencing the changes of reservoir rocks and fluid properties during fire flooding. In order to subdivide the changes in each phase of fire flooding, the paper uses the thermogravimetric-differential scanning calorimetry method to characterize oxidation process of crude oil, and studies rock evolution and its influences on reservoir properties at different temperature intervals by using X-Ray diffraction and back scattered electron imaging technologies. The study results show that there are 4 critical temperatures during fire flooding, i.e., crude oil oxidation activation, high-temperature combustion threshold, thermal activation of rock, and deep rock metamorphism, and the rock evolution can be divided into 5 phases such as formation preheating, low-temperature oxidation of crude oil, medium-temperature crude oil oxidation and clay decomposition, high-temperature crude oil oxidation and clay sintering, and deep metamorphism of non-clay minerals, among which the phases of high-temperature crude oil oxidation and clay sintering are the maximum mobility period during the evolution with the released heat of crude oil combustion accounting for about 60% of the total released heat, and the clay minerals have sintering, resulting in the obvious changes of reservoir pore structures and properties Related Articles | Metrics

Experimental Simulation of Initial Water Saturation Forming Process in Tight Reservoirs: A Case Study of Chang 7 Tight Oil Reservoir in Ordos Basin, NW China TIAN Jian, KANG Yili, LUO Pingya, YOU Lijun 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180611 Abstract ( 142 )   PDF (871KB) ( 445 )   Save The crude oil charging degree is high in the Chang 7 tight oil reservoir of Yanchang formation in Ordos basin, the average oil saturation is more than 70%, and ultra-low water saturation is observed in the reservoir locally. Previous researchers seldom considered the influence of the back pressure at the outlet end of the core on oil and water flowing behavior when they carried out crude oil charging experiments on tight cores. During the displacement, only the fluid around the inlet formed the pore pressure under displacement pressure to overcome flow resistance and the pressure at the outlet end was atmospheric pressure, resulting in significant differences between the water saturation obtained from the displacement and the water saturation gained from logging analysis. In order to study the influences of back pressure on ultra-low water saturation forming process during crude oil charging in tight oil reservoirs, the core from Chang 7 tight reservoir of Yanchang formation is selected to carry out a single-phase flowing simulation experiment under different pore pressures with added back pressure at the outlet end, and crude oil charging experiment is performed based on the selected back pressure. The experiment result shows that with the added back pressure the required displacement pressure gradient significantly decreases during the single phase flow, whereas, with the same low pressure gradient a larger flowing rate can be measured. During two phase displacement, the obtained water saturation with the added back pressure is consistent with the result interpreted by logging data, indicating that the forming process of ultra-low water saturation can be represented under the added back pressure. It is considered that an added back pressure is of great significance to improve the test efficiency of liquid flowing experiment for tight cores and to simulate the ultra-low water saturation forming process during crude oil charging Related Articles | Metrics

Injection Parameter Optimization of A Viscosity-Controlled Gel System LYU Hang, LIU Xiangbin, WANG QingguoZHOU QuanWANG Li 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180612 Abstract ( 117 )   PDF (1335KB) ( 312 )   Save After the polymer flooding, Daqing oilfield is characterized by developed preferential flow path, serious channeling and difficulties in efficient production. In order to maintain the sustainable and effective development of the oilfield, researches have been carried out for the technologies of profile modification, water plugging and flooding. Regarding the requirement of profile modification and water plugging, a viscosity-controlled gel system is developed. The initial viscosity of the system is less than 20 mPa·s, during 10~40 days, the system viscosity is less than 300 mPa·s and the gel viscosity is above 2 500 mPa·s. The data from cored wells after polymer flooding are used to design a physical model. The optimal injection volume determined by orthogonal experimental design is 0.10 PV, the injection concentration is 1 000 mg/L and the injection rate is 0.6 mL/min. The actual application shows that after modification the shunt rate of high-permeable layer reduces from 66.9% to 0.7%, that of medium-permeable layer increases from 33.0% to 85.0%, that of low-permeable layer improves from 0.1% to 14.3%. The system has low pollution to medium and low permeable layers and can effectively plug the high-permeable layer, which can meet the demands of field operation Related Articles | Metrics

Water Saturation Correction Through Sealed Coring in Low-Permeability Tight Gas Reservoirs: A Case Study from Huagang Formation in Xihu Sag, East China Sea Basin FU Yanxin 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180613 Abstract ( 123 )   PDF (891KB) ( 331 )   Save In Xihu sag of East China Sea basin, the gas saturation evaluation for low-permeability tight gas reservoirs is always the key difficulty in exploration and development. The conventional core analysis method such as mercury injection is difficult to get accurate gas saturation of low-permeability tight gas reservoirs. Compared with conventional core analysis, the measured water saturation through sealed coring is more approaching to the actual situation. But water volatilization is a problem. In order to accurately calibrate the gas saturation, the paper analyzes the main factors influencing the water saturation through sealed coring, compares 3 core treatment methods, proposes a new water saturation correction method considering the distortion of rock pores and based on the experiment of sealed-coring volatile quantity of low-permeability tight gas reservoirs, and performs water saturation correction through sealed coring in WELL-5 in Xihu sag with the total correction of about 10%. The results show that the new correction method is simple and practical, which is suitable for the sealed coring saturation correction for low-permeability tight gas reservoirs in Xihu sag of East China Sea basin Related Articles | Metrics

Study on Equivalent Flow Circle LI Chuanliang1, DENG Peng1, ZHU Suyang1, LIU Donghua2 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180614 Abstract ( 211 )   PDF (737KB) ( 465 )   Save There are strict production calculation formulas for simple round formations or linear formations, and the formulas are similar to Ohm’s law. However, it is difficult to calculate the production of complicated formations because there is no analytical formulas, resulting in the difficulties in production management. In order to study the flow of complicated formations, the paper proposes an equivalent flow resistance method which considers a complicated formation as a combination of round formation and linear formation equivalently, then calculates the flow resistance of the complicated formation according to the principle of water-electricity similarity, finally the production formula is established for the complicated formation based on the Ohm’s law. But during the process, there are still some divergences. Some researchers propose to use a larger flow circle, and some others are likely to use a smaller one. Obviously the larger flow circle overestimates the flow resistance and underestimates the flow rate of wells, while the smaller flow circle underestimates the flow resistance and overestimates the flow rate. The influence of the equivalent circle processing method on the calculated production of horizontal wells is relatively small but is significant on the calculated production of vertical wells. The study shows the equivalent processing method of the smaller flow circle is more reliable than that of the larger one. It is suggested that the equivalent processing method of smaller flow circle should be adopted in the study and application of the equivalent flow resistance method Related Articles | Metrics

Calculation Method of Formation Quality Factor Based on Continuous Wavelet JINAG Li, MAO Haibo, LIU Hongjie, WANG Xiaotao, XIAO Yanling 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180615 Abstract ( 161 )   PDF (1777KB) ( 382 )   Save Continuous wavelet is a kind of advanced time-frequency analysis method that can extract information about time and frequency of seismic data accurately. Using continuous wavelet time-frequency analysis method, seismic data can be decomposed into multi-frequency scale data, and the exponential decay factor for amplitude versus time in different frequency scale can be calculated, the slope of exponential decay factor versus frequency curve can be calculated by using regression analysis method and finally formation quality factor can be calculated. The applications of model, VSP, uphole survey and seismic data indicate that compared with the methods of conventional spectral ratio and frequency shifting, the calculation method of formation quality factor based on continuous wavelet is a kind of high-precision, high noise immunity method which can be used in formation quality factor calculation for various seismic data Related Articles | Metrics

Productivity Analysis and Fracturing Design Optimization of Fractured Horizontal Well in Tight Gas Reservoirs SUN Yuanwei1, CHENG Yuanfang2, SHI Fengxia1, WANG Yanli1, YIN Shuming1 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180616 Abstract ( 99 )   PDF (1115KB) ( 202 )   Save Tight gas reservoirs are characterized by low permeability, narrow pore throats and extremely poor flowing conditions. Based on the influence of stress sensitivity on reservoir permeability, this paper establishes a new mathematical flow model for horizontal well fracturing in tight gas reservoirs and then obtains semi-analytical solutions of dimensionless pressure considering wellbore storage effect through Laplace transform. Based on the verification of the validity of the model, the productivity vs. time curves are plotted for staged fracturing in horizontal wells, the factors influencing productivity are analyzed and orthogonal experiment is designed to determine the main controlling factors. The results show that when the fracture half-length is 140 m and the density of fractures is 6 per 1000 m, the optimum production can be obtained by increasing the permeability of the stimulated area. The conclusion is of guiding significance for the design of horizontal well fracturing in tight gas reservoirs Related Articles | Metrics

VTI Media Kirchhoff Pre-Stack Depth Migration Technology and Its Application XIA Changliang1,2, WANG Yongming2, XIA Mili2, LIU Hongjiu2, HU Hao2, WANG Xiangchun1 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180617 Abstract ( 166 )   PDF (2199KB) ( 663 )   Save Regarding the multiple solutions of velocity inversion of pre-stack depth migration（PSDM）and the mismatch between horizon calibration and migration results, and taking the seismic data of a district with complex structures in Iraq as a case, the paper detailedly introduces the VTI media (Transversely Isotropy with vertical axis of symmetry) Kirchhoff PSDM technology and its application and notices. The paper proposes a combined method which uses interval velocity inversion with interval-stripping velocity correction method and logging curve trend constrain method to solve the multiplicity problem; obtains the initial interval velocity through constrained velocity inversion(CVI) in a root-mean-square velocity field of pre-stack time migration to ensure the accuracy of the initial interval velocity field and effectively decrease the iteration numbers of interval velocity inversion with interval-stripping velocity correction method; and solves the mismatch between the migration results and horizon calibration by using VTI media migration. The actual application results show that the above mentioned Kirchhoff pre-stack depth migration process and its notices can effectively improve the work efficiency of pre-stack depth migration and obtain more reliable velocity model in depth domain, and can increase the accuracy of velocity inversion to obtain horizons corresponding to drilling stratification Related Articles | Metrics

Theoretical Derivation of Logistic and Generalized-Arc-Tangent Production Decline Equations CAI Xidong, GAO Wenjun, SONG Hongxia 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180618 Abstract ( 129 )   PDF (803KB) ( 205 )   Save To reveal the flow characteristics of Logistic and Generalized-Arc-Tangent production decline equations, the paper selects a special oil-phase relative permeability relation and deviates Logistic and Generalized-Arc-Tangent production decline equations and its corresponding water-phase relative permeability formula according to the derivation process of Arps production decline equation. The results show that the type of production decline is mainly determined by the characteristics of oil-water two-phase flows under the condition of maintaining formation pressure by water injection. The relative permeability relations of oil and water phases take the water saturations at the outlet as variables, which complies with the industrial standards of relative permeability relations and avoids the defects of the pseudo-relative permeability relations using the average water saturation as a variable during previous decline equation derivation. The actual applications in Qiuling oilfield and Block Wen-5 in Tuha oilfield show that the actual production is consistent with the results obtained from the production decline equation determined by relative permeability relations of oil and water phases, respectively Related Articles | Metrics

Comprehensive Fluid Prediction with Multi-Wave Attribute Seismic Technology in Wellblock S48, Tahe Oilfield YANG Zichuan1, TAO Lei2, LI Haiying1, YU Guangming3, ZHANG Hongying4 2018, 39 (6):  1-1.  doi: 10.7657/XJPG20180619 Abstract ( 107 )   PDF (1797KB) ( 427 )   Save With the development of the seismic anisotropy theory, the multi-wave technology plays an increasingly important role in the reservoir fluid detection. Compared with longitudinal waves, the acquisition of longitudinal waves and transverse waves in multi-component seismic provides the possibility of improving the prediction accuracy of reservoir fluid. Based on the 3D 3-component seismic data gathered from Wellblock S48 in Tahe oilfield and regarding the fractured-vuggy carbonate reservoirs, the analyses on vp/vs, Poisson’s ratio, weakness ratio and inversed parameters, Lame Constant and density are carried out and fluid prediction is performed by using multi-wave attribute seismic technology. Compared with conventional P-wave frequency spectrum analysis technique, the multi-wave seismic prediction technology can improve the accuracies of reservoir prediction and hydrocarbon identification, and reduce the uncertainties of conventional P-wave fluid prediction method Related Articles | Metrics