Lithologic Reservoirs

Velocity es timation and modeling technique is a key issue in exploration seismic. As a typical inversion problem, velocity estimation should be carried out under the framework of Bayesian estimation. However, a series of techniques for velocity analysis and modeling are developed by the petroleumindustry. In viewof the present situation of research and application of velocity estimation and modeling technique, we try to analyze the current velocity estimation methods under the framework of Bayesian estimation. All the existing velocity estimation methods can be incorporated into the following two objective functions: the best correlation criterion （the best focusing criterion） in the image-domain or the least error criterion in the data-domain. The gradient-guided local optimization method and Monte Claro method can be used to estimate the seismic velocity in different scales. Under this framework, we can analyze the common features of all the currentmethods, and develop new methods and techniques for velocity estimation.

Theoretical analysis and comparison of seismic wave inversion and imaging methods

REN Haoran， WANG Huazhong， HUANG Guanghui

2012, Vol.24(5): 12–18 Abstract ( 767 ) PDF (564 KB) ( 995 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.002

Based on the mathematical and physical theory of wave equation, the full waveform inversion, travel-time tomography, least squares migration and migration velocity analysis can be included into a same inversion frame. Based on Bayes theory, this paper analyzed and compared these methods. It is proved that the full waveform inversion can use most seismic information, but the overlying of different information increases the difficulty of its usage. Under the guidance of signature waveform inversion, the characterized information were extracted to carry out seismic inversion, and several schemes were analyzed and compared theoretically.

Non-Darcy flow cannot occur in low permeability reservoir： Discussion on “High rate non-Darcy flow is easer to occur in low permeability reservoir?”

DOU Hongen

2012, Vol.24(5): 19–21 Abstract ( 488 ) PDF (515 KB) ( 629 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.003

No scholar once though that high velocity non-Darcy flowis easer to occur in lowpermeability reservoir in previous research results. Forchheimer equation is still used to gas high velocity flowin gas reservoirs for long time, and the gas flowequation of non-Darcy flowwould be derived fromthe equation. The author derived a theoretical equation of turbulence coefficient of non-Darcy flow, and the theoretical equation form accords with empirical equation when comparing the both equations. It is proved that empirical equation of turbulence coefficient of Forchheimer equation is right. Some people thought that empirical equation of turbulence coefficient of Forchheimer equation is not right, and it rooted in a wrong relationship between Reynolds number with resistance factor of turbulence flow, which was used. A linearization solution method of turbulence coefficient of Forchheimer equation is also expressed.

Hydrocarbon accumulation rules of Wangchang Oilfield in Qianjiang Sag

GUO Feifei， ZHANG Fan， ZHANG Wu， TANG Wenxu

2012, Vol.24(5): 22–26 Abstract ( 528 ) PDF (756 KB) ( 672 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.004

Based on the study of hydrocarbon generation potential, sedimentary system, reservoir conditions, tectonic conditions, temperature-pressure conditions, hydrocarbon distribution, the history of hydrocarbon generation, expulsion and migration of Qianjiang Formation in Wangchang Oilfield, the hydrocarbon accumulation rules were analyzed. The result shows that there are favorable hydrocarbon accumulation conditions in WangchangOilfield, and the hydrocarbon accumulation is mainly controlled by the distribution of hydrocarbon source rocks，favorable sand bodies, faults and the revolution of anticline structure. The hydrocarbon accumulation model is established, which is self source and mixed sources, vertical and lateral migration and multi-stage formations of hydrocarbon reservoir. The reservoirs are located around the hydrocarbon generation sags, the hydrocarbon is mainly distributed in the Wanghcang anticline belt, the active period of fault is in accord with the period of hydrocarbon accumulation period, the hydrocarbon is migrated through faults and sand, and the migration pattern and accumulation direction of hydrocarbons are determined by the lateral sealing ability of faults.

Essence of diapir and its relationship with natural gas accumulation in Yinggehai Basin

HAN Guangming， ZHOU Jiaxiong， PEI Jianxiang， WANG Lifeng

2012, Vol.24(5): 27–31 Abstract ( 500 ) PDF (965 KB) ( 776 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.005

Diapir is a specific abnormal geologic body in Yinggehai Basin of northern margin of South China Sea. According to the study, it is considered that diaper is a combination of deep mud diaper and shallowfluid diaper, and it has been in a dynamic equilibrium state and it will keep this state for a long time. Different types of diapir has different exploration potential, and the high and middle energy diapir has better exploration potential. For the same type of diaper, its non-collapse part has better exploration potential.

Hydrocarbon accumulation condition of superimposed rift-subsidence basin:A case study from Lishui-Jiaojiang Sag in the East China Sea

TIAN Bing，PANG Guoyin，WANG Qi，TANG Jun， LIAO Peng

2012, Vol.24(5): 32–37 Abstract ( 489 ) PDF (948 KB) ( 778 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.006

Lishui-Jiaojiang Sag is the representative offshore superimpose rift-subsidence basin of China. Paleocene is identified as the main faulting period of the sag, which can be divided into four episodic rifting. There was lacustrine environment in the first episodic rifting, and then the sedimentary environment changed into marine environment. There are three groups of hydrocarbon source rocks and three sets of reservoir-cap assemblage. The lacustrine mudstone of Yueguifeng Formation has high abundance of organic matter, mainly belongs to the type Ⅱ, has good potential of hydrocarbon generation, and is regarded as the main hydrocarbon source rocks of this area. Paleocene sandstone is the main reservoir of the sag, sandstone reservoirs of Lingfeng Formation and Yueguifeng Formation belong to the type Ⅲ and Ⅳ, sandstone reservoirs ofMingyuefeng Formation belong to the type Ⅲa and Ⅱb, reservoir property is changed by the top-sealing abnormal high pressure system. The reservoir-cap assemblage composed by the early faulted （fan） delta, lakeside and coastal sandstone together with the shallowsea mudstone of the top of Lingfeng Formation and the bottom of Mingyuefeng Formation has nice exploration potential, because the main hydrocarbon source rocks and the abnormal high pressure system approach the assemblage and there are favourable reservoir-cap configuration conditions. The favorable zones predicted are located above of the hydrocarbon generating center of Lishui-Jiaojiang Sag, on both sides of the Lingfeng buried hill and the westen slope of West Subsag ofLishui Sag, and can be divided into three major categories and 11 favorable structure belts.

Hydrocarbon accumulation conditions of Chang 2 oil reservoir set in Jiyuan area, Ordos Basin

HE Jinxian，YAN Jinpeng，QI Yalin，ZHANGXiaoli，ZHU Beier，QIN Yulu

2012, Vol.24(5): 38–42 Abstract ( 593 ) PDF (716 KB) ( 665 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.007

Jiyuan area is one of the key oil and gas exploration area within the basin. Based on the research of source rocks, reservoir rocks, hydrocarbon migration and traps, this paper synthetically analyzed the hydrocarbon accumulation conditions of Chang 2 oil reservoir set in Jiyuan area. The result shows that hydrocarbon of Chang 2 oil reservoir set mainly comes fromChang7 source rocks. The reservoir in the study area is mostly underwater distributary channel sand bodies, and sandstone is mainly composed of arkose, lithic arkose, with little feldspathic lithic sandstone, so it belongs to moderate porosity and low permeability reservoir. Compaction, cementation and dissolution are the main diagenesis types. The abnormal high pressure from Chang 7 oil reservoir set drives the oil generated from Chang 7 source rocks up to Chang 2 oil reservoir set. The oil in Chang 2 oil reservoir set is mainly trapped by structural-lithologic trap, with local area by structural trap and lithologic trap. The thick interdistributary mudstone developed in Chang 2 oil reservoir set plays the necessary role as the shield and cap rock ofChang2 oil reservoir set.

Gas reservoir characteristics of the second member of Xujiahe Formation and prediction of favorable gas bearing zones in Penglai area, central Sichuan Basin

LAI Jin， WANGGuiwen

2012, Vol.24(5): 43–49 Abstract ( 548 ) PDF (1042 KB) ( 542 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.008

The second member of Xujiahe Formation in Penglai area of central Sichuan Basin is of great potential for gas exploration, but on the other hand, the reservoir is also characterized by lowporosity and lowpermeability, complicated pore structure and well logging response characteristics, so the exploration and development effect is influenced by these existing problems. In order to improve the oil and gas exploration degree and to find more high-quality reservoirs and favorable gas bearing zones, this paper studied the generation, storage, capping, migration, trapping and preservation of the second member ofXujiahe Formation together with their matching relationship with each other, and predicted the favorable gas bearing zones bymaking full use of drilling, logging, cores and slices data based on the previous research results. The research results showthat:①the source rocks are of great potential for hydrocarbon-generating, and Penglai area is located in the superior place for gas accumulation with effective trap; ② the mudstone of the third member of Xujiahe Formation can be effective cap rocks;③ source-reservoir-cap rock assemblage is in a good form, the relatively stable hydrodynamics are in good conditions for gas accumulation. The reservoirs of the second member of Xujiahe Formation are generally in the favorable tectonic and sedimentary facies belt. Sedimentation is the foundation for reservoir forming, diagenesis is the key points for reservoir quality, while the fracture development determines the productivity of reservoirs. The prediction of the favorable gas bearing zones can provide certain references for next exploration deployment in the study area, and it is favorable for the petroleumexploration in some areas with similar reservoir characteristics

Fault characteristics of Chang 9 reservoir and its impact on reservoir in Jiyuan Oilfield

CHENG Liangbing， QU Chunxia， GOU Yongjun， HE Youan， WANG Jin， WANG Fang

2012, Vol.24(5): 50–54 Abstract ( 539 ) PDF (930 KB) ( 507 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.009

Formation changes and structural mutation were found in part of adjacent wells in the production process of Chang 9 reservoir in Jiyuan Oilfield. By seismic interpretation, strata correlation and core observation, 21 NWW normal faults developed in Jiyuan area were found. The time and space of Tianhuan Depression and hydrocarbon-generating peak of Chang 7 hydrocarbon-generating rocks are matched, which promotes the hydrocarbon lateral migration and accumulation, so the reservoir is relatively enriched in eastern part of the depression. The reservoir was readjusted after fault formation, which results in the destruction of reservoir belowthe faults.

Oil sources and accumulation analysis of Chang 9 and Chang 10 oil reservoir set in Yingwang area, Ordos Basin

HE Yanbing，FU Qiang，JIN Yan，LI Yuanhao

2012, Vol.24(5): 55–60 Abstract ( 494 ) PDF (919 KB) ( 378 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.010

Recently, newreservoirs have been found in Chang 9 and Chang 10 oil reservoir set of Triassic Yanchang Formation in Yingwang area, Ordos Basin. Based on source rocks characteristics, oil-source correlation and accumulation patterns, it is considered that even though the source rocks of Chang 9 oil reservoir set is a set of good source rocks, it contributed little to the hydrocarbon accumulation of Chang 9 and Chang 10 oil reservoir set. The oil in Chang 9 and Chang 10 oil reservoir set in Yingwang area are mainly from the source rocks of Chang 7 oil reservoir set in Huachi-Taibai-Zhengning-Yingwang area. Abnormal high pressures produced during the diagenetic evolution are the main force for hydrocarbon migration. Pores and fractures are the main migrating system, which allows oil tomigrate vertically along fractures and inject laterallywhen it met sandstone.

Origin of super-low permeability sand bodies of Chang 6 oil reservoir set in Huaqing area, Ordos Basin

WANG Hongbo， LI Xiangbo， LIAO Jianbo

2012, Vol.24(5): 61–64 Abstract ( 479 ) PDF (720 KB) ( 507 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.011

The theory of sandy debris flowis partial negation and improvement of deep-water sediments concepts such as Bouma sequence and turbidite fan. Based on crop, core observation, sample analysis, combined with sand body characteristics, it is considered that the sandy debris flow is the dominant sediments of Chang 6 oil reservoir set in Huaqing area, which changes the traditional concept of that there is only small-scale turbidite in the center of the lake basin. The further study suggested that the sandy debris flow is mainly controlled by deep water sedimentation slope break belt. The thick-bedded super-lowpermeability sand bodies of Chang 6 oil reservoir set in Huaqing area is typical gentle slope sandy debris flowsediment.

Fracture characteristics of Chang 8 reservoir of Yanchang Formation in Xiasiwan area, Ordos Basin

LI Zhe1， TANG Jun， ZHANG Yunpeng， ZHANG Fengbo， YANGZ hengguang， WU Xuechao

2012, Vol.24(5): 65–70 Abstract ( 528 ) PDF (1009 KB) ( 583 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.012

Chang 8 reservoir of Yanchang Formation in Xiasiwan area of Ordos Basin is a typical lowporosity and low permeability sandstone reservoir. The fractures have a significant impact on hydrocarbon accumulation and the oilfield development effect as the fractures can be as the effective space and the main seepage channel of low permeability reservoir. Therefore, the characteristics and the identifications of the fracture are the key research work to the evaluation of the reservoir in this area. Based on regional geology, well logging, well drilling and core data in Xiasiwan area, fracture characteristics were analyzed by the study of tectonic stress field, slices and conventional logging analysis. Through the comparison between the palaeotectonic stress field and the modern tectonic stress field, the favorable distribution position of the fractures is analyzed and the main orientation affected by regional tectonic movement is NE 70°, which can provide a strong basis for suitable arrangement ofwell patterns. The data of rock slices indicate that micro-fractures are well developed and have better connectivity. By combiningwith the intersection identification method of deep-probe resistivity and acoustic time and the response characteristics of conventional logging for fractures, the single well fractures can be identified, and it is concluded that conventional logging data is more inclined to identify the fractures developed inmudstone.

Provenance analysis of Chang 9 oil reservoir set in Longdong area, Ordos Basin

NIU Xiaobing，LIANGXiaowei，XIN Honggang，LI Tingyan，DAN Weidong，WANGChangyong

2012, Vol.24(5): 71–75 Abstract ( 529 ) PDF (826 KB) ( 498 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.013

There maybe exist multiple source supply during the sedimentation period of the Chang 9 oil reservoir set in Longdong area. Provenance analysis is not only the basis of study the delta development characteristics of Chang 9 oil reservoir set, but also the foundation for evaluation and prediction of sand bodies. Based on the relative change of quartz content, heavymineral assemblages, quartz cathodoluminescence, debris content and paleosalinity recovery, it is considered that the deposition is controlled by the sources from the southwest, the northwest, the south and the northeast of Longdong area at the same time. The southwest of the study area is the main source area, followed by the south, the northwest and the northeast. The parent rocks in the southwest are middle-high grade metamorphics and volcanics in the Qilian tectonic belt, while the source in the south, the northwest and northeast is granite and low-middle grade metamorphics fromthe Southern Qinling tectonic belt, Alaschanica ancient land and Yinshan ancient land respective. The sediments that come fromdifferent directions converge at the area ofYuancheng-Huachi-Majiabian-Taibai.

Study on characteristics of the Paleocene overpressure seal and its sealing ability in Dongying Depression

WANG Xudong，ZHA Ming，QU Jiangxiu，GAO Changhai，CHEN Zhonghong，ZHANG Shouchun

2012, Vol.24(5): 76–82 Abstract ( 505 ) PDF (883 KB) ( 383 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.014

Observed pressure reveals that overpressure is widely developed in the Paleocene in DongyingDepression, Eastern China. According to logging responses of overpressure mudstones, the vertical distribution of overpressure seal is identified. On this basis, its petrological characteristics and sealing ability were systematically studied. The result shows that the burial depth for the Paleocene overpressure seal top is mainly 2 400～2 800 m and became shallower from the center to edge of the sag and the central uplift in the plane. The lithological composition of the overpressure seal is formed by a group of dark graymudstone, calcareous mudstone and sandymudstone, ofwhich the average sand-clay ratio is 0.092, the thickness is 500～900 m and the maximal thickness of the single mudstone is greater than 10 meters. Whole rock X-ray diffraction shows that the mudstones of the pressure seal contain large amounts of carbonate minerals and clay minerals. Mudstone diagenesis reaches the rapid transformation of the illitemontmorillonite interlayer minerals, and corresponds to the mass carbonate minerals during the first and second stage. The overpressure seal could close surplus pressure greater than 14 MPa, which had a close relation with high displacement pressure （average 5.45 MPa）. Besides, thickness and diagenetic grade of the overpressure seal are important influencing factors for its sealing ability.

Reservoir characteristics and controlling factors of dolomitic rocks of Fengcheng Formation in Wufeng area, northwestern margin of Juggar Basin

YIN Jianguo， DINGChao， GU Qing， WANGZhongjun， WANGGuiwen， SHI Ji’an

2012, Vol.24(5): 83–88 Abstract ( 552 ) PDF (1149 KB) ( 624 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.015

Based on the investigation of cores, rock slices and scanning electronic microscope, this paper investigated the reservoir properties and controlling factors of the Permian Fengcheng Formation in Wufeng area, northwestern margin of Juggar Basin. The result shows that siltstone, mudstone and tuff developed in the study area were dolomitized in various extents. Dolomite crystal developed mainly fine crystal and powder crystal. The distribution patterns of dolomite crystal in tuffaceous or mud matrix show three different types: lump, satellite and along bedding or fracture. Intergranular pores, intercrystalline pores, dissolved pores and fractures developed mainly in Fengcheng Formation. Both of dissolved pores and fractures are the main reservoir space. Deposition, dolomitization and tectonism affect the reservoir properties together. Depositional setting determines the distribution of dolomitic rocks, dolomitization enhances rock brittle, and large amounts of fractures developed under tectonismas reservoir spaces and percolation channel, which makes dissolved pores developed around.

Reservoir differences of the Ordovician Yingshan Formation in the northern slope of Tazhong

ZHENG Jian，LIN Xin，WANG Zhenyu，QU Haizhou，YANG Fei

2012, Vol.24(5): 89–93 Abstract ( 436 ) PDF (925 KB) ( 580 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.016

The marine carbonate rocks of the Ordovician Yingshan Formation are regarded as the main producing formation and reservoir in the northern slope of Tazhong. The depositional environment and lithology in different well areas are very similar, while the reservoir properties show a great difference. This paper applied the information of interstratal karst, buried karst, tectonic action and fluid property to analyze the reservoir differences of Yingshan Formation. The result shows that the block differences of cavity development in the interstratal karst period lead to the reservoir differences, fracture development leads to the differences of fluid migration pathways, and the differences of fluid migration direction of the third buried period eventually result in the differences in reservoir development and hydrocarbon accumulation.

Application of simulated annealing static correction technology in the low S/N area

CUI Hongliang， BAI Xuming， YUAN Shenghui， CHENGZhanzhan， GE Daiwei， WANGXiaodong

2012, Vol.24(5): 94–97 Abstract ( 475 ) PDF (864 KB) ( 477 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.017

When residual statics is small, using a linear method can solve the static correction problemin conventional seismic data processing. In the regions of complex near-surface condition and lowS/Nseismic data, there are still a lot of residual statics after conventional static correction. Traditional reflection wave residual static correction is easy to fall into local extreme, and “cycle jump” phenomenon appears. Fast simulated annealing static correction technique can solve large residual statics problem, and it is especially suitable for the regions of complex near-surface condition and lowS/Nseismic data.

Application of frequency attenuation attributes to oil and gas exploration in deep carbonate rocks

YANG Lu，HE Zhenhua，WEN Xiaotao，YANG Xiaojiang，SHENG Qiuhong

2012, Vol.24(5): 98–102 Abstract ( 543 ) PDF (803 KB) ( 613 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.018

According to deep burial depth, uneven oil and gas distribution of carbonate reef flat lithologic reservoir of Changxing Formation in BL area, this paper put forward a train of thought for hydrocarbon detection which combined frequency attenuation attributes and low frequency ad joint-shadow phenomenon. This paper first introduced the principle of frequency attenuation attributes and low frequency ad joint-shadow phenomenon; secondly established geological model combined with the reservoir physical parameters of Changxing Formation in BL area, and simulated and analyzed the seismic response characteristics of the reservoir by using viscosity-diffusivity wave equation. The model analysis result shows that it is feasible to detect gas-bearing properties of reservoir by using frequency attenuation attributes and low frequency ad joint-shadow phenomenon. Application of real data demonstrates that frequency attenuation attributes and low frequency ad joint-shadow phenomenon has good instruction to the reservoir, and improved the accuracy of reservoir prediction and fluid detection, which can provide a way for oil-gas identification and fluid detecttion of carbonate reef flat lithologic reservoir and similar reservoirs of Changxing Formation in BL area.

Application of AVO fluid inversion technique to hydrocarbon detection in northeastern Sichuan

LI Ning， SU Yun， TIAN Jun， QIN Guangsheng

2012, Vol.24(5): 102–106 Abstract ( 495 ) PDF (1053 KB) ( 595 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.019

As traditional AVOtechniques can not be used to visually evaluate the hydrocarbon potential of the reservoir, so the extracted AVO attributes are not well in accord with the gas-bearing properties of the actual wells. This paper proposed AVO fluid inversion to analyze the gas-bearing properties in northeastern Sichuan. This technology was successfully applied in the fourth member of Xujiahe Formation in one area of northeastern Sichuan. The result was consistent with case of actual wells, and good results have been achieved, which affords a favorable evidence for reservoir prediction in this area.

Injection-production parameters optimization in single well condensate gas huff and puff

WANGBing， LIU Yuetian， MA Cuiyu， LI Erpeng， ZHANGTingjing

2012, Vol.24(5): 107–110 Abstract ( 473 ) PDF (801 KB) ( 623 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.020

Single well condensate gas huff and puff can improve oilfield recovery ratio greatly, so the injection-production parameters optimization in single well condensate gas huff and puff has important production guiding significance. Based on the study of the effect of single well condensate gas puff and huff in reservoir B, this paper established the compositional simulation model, and analyzed the influencing factors to single well condensate gas huff and puff, including condensate gas cycle injection volume, injection rate, well shut-in time and production rate. The injectionproduction parameters of single well condensate gas huff and puffwere optimized with the orthogonal experiment design method. The optimized injection-production parameters are as the following: the injection volume is 283.2×104 m3, injection rate is 11.3×104m3/d, well shut-in time is 10d and production rate is 1 590 m3/d.

Study on gas-oil diffusion coefficient in porous media under high temperature and high pressure

YE Anping， GUOPing， WANGShaoping， XU Yanmei， CHENGZhongzhao

2012, Vol.24(5): 111–115 Abstract ( 557 ) PDF (807 KB) ( 681 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.021

The study ofmolecular diffusion coefficient for gas-oil systemfocuses mostly on the single gas-oil system, and the diffusion coefficient is measured in the PVT tube under lowpressure or lowtemperature. Under the circumstances, this paper tested the effective diffusion coefficient between the gas injected and oil in porous media under high temperature and pressure, and also tested the diffusion coefficient of gas-condensate oil systemand gas-heavy crude oil systemin the full diameter core under 60℃and 20MPa respectively. The results showthat the components of crude oil have a little influence on the diffusion coefficient. The gas diffusion coefficient in condensate oil is higher than that in heavy oil. The diffusion coefficient follows a power function and increases with the increasing of time, and the curve flattens gradually finally.

Prediction method of polymer flooding operation cost based on gray principal component analysis

ZHOU Qing

2012, Vol.24(5): 116–119 Abstract ( 415 ) PDF (684 KB) ( 400 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.022

Polymer flooding has characteristics of high oil production rate and short production duration, complicated operation cost change rule, and its operation cost structure and prediction method are different from water flooding. Scientific prediction of polymer flooding operation cost is essential to control the cost of operations and establish a cost plan. Combining with the characteristics of polymer flooding development, this paper applied gray system theory and principal component analysis method to select the influencing factors, and then established prediction model to predict polymer flooding operation cost. The practical application proves that this method can be used to predict polymer flooding operation cost better and achieve the purpose of improving the prediction accuracy. It can provide a scientific basis for the rational preparation of development planning program.

Application of Lorenz curve to injection profile in Xing 6 district

HU Wei， LIU Dehua

2012, Vol.24(5): 120–123 Abstract ( 509 ) PDF (728 KB) ( 587 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.023

After forty-three years ofwaterflood development of the reservoirs in Xing 6 district, it is nowin high water cut stage of development, and the water absorption of reservoirs is seriously uneven. Compared with conventional injection profile, Lohrentz curve is used to study that the uneven extent of injection profile of twowells in Xing 6 district is caused by reservoir heterogeneity and human factors, and analyze the differences of injection profiles before and after adjustment and the differences of injection profile in different times. Based on the analysis of Gini Coefficient in Lohrentz curve, “nonuniformity coefficient” was introduced to measure water absorption of different layers and the uneven extent of injection profile. It is considered that the uneven extent of injection profile in Xing 6 reservoirs is becoming more and more serious. Meanwhile, some corresponding adjustment measures were offered. All these provide a foundation for the further development and relevantmeasure adjustment in this oilfield.

Areal sweep efficiency of staggered well pattern of horizontal wells in low permeability reservoirs

ZHOU Ying， TANGHai， LU Dongliang， ZHAOChunming， LIAOXingwu

2012, Vol.24(5): 124–128 Abstract ( 626 ) PDF (825 KB) ( 762 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.05.024

Bymeans of characteristics of the staggered well water flooding exploitation in lowpermeability reservoirs, and on the basis of streamtubemodel and the Beckley-Leverett equation, the areal sweep efficiency formula and water breakthrough time formula considering start-up pressure gradient were derived for the staggered well pattern of horizontal wells. This theory solved the problems of theoretical calculation of areal sweep efficiency and water breakthrough time on the state of non-Darcy flow. The case study shows that the theoretically calculated results are very close to the reservoir. So this method is scientific and reasonable, and it can be used to quantitatively characterize the reservoir produced degree in staggered well pattern and provide theory basis for development and evaluation of lowpermeability reservoirs.