Lithologic Reservoirs

Cave reservoir is the main reservoir type in the carbonate rocks well developed area in western China. This paper systematically recommended some fundamental researches on the recognition of carbonate cave reservoirs carried out by the authors and recognition methods obtained, including numerical simulation, wave field analysis, newcognition of cave reservoirs identifiability, application of amplitude, improvement of reservoir inversion and frequency diversity analysis.

Nuclear magnetic resonance logging observation model for heavy oil reservoir and its application

LIU Diren， YIN Qiuli， YUAN Jihuang， CHEN Jian， XIE Weibiao

2012, Vol.24(2): 7–10 Abstract ( 453 ) PDF (382 KB) ( 631 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.002

Due to the high viscosity and high density of heavy oil, it is difficult to obtain good result by using nuclear magnetic resonance logging observation model for conventional reservoirs in heavy oil field. Based on the principle of nuclear magnetic resonance logging and characteristics of heavy oil reservoir, this paper discussed how to choose the parameters of TW , TE and NE, and obtained effective log data by optimizing observation model for heavy oil reservoir. Taking JMS heavy oil area as an example, the nuclear magnetic resonance logging data were applied to carry out log interpretation for heavy oil reservoir, and good results have been obtained.

Seismic facies and sedimentary facies of the lower segment of Sangonghe Formation in Bohu Depression, Yanqi Basin

GUO Wei， LI Xiaogang， LIU Shangjun， LIN Sheqing， YAN Yongxin

2012, Vol.24(2): 11–15 Abstract ( 530 ) PDF (541 KB) ( 636 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.003

In order to study the favorable distribution area of lithologic traps in Bohu Depression ofYanqi Basin, based on seismic sequence division, the amplitude, frequency, continuity, internal structure and external formof seismic reflection wave were applied to analyze the seismic facies in the study area, and the seismic facies of the target zone can be divided into six types. The seismic facies is transformed into sedimentary facies bymeans of well-seismic combination. The result shows that six types of sedimentary facies are distinguished in the lower segment of Sangonghe Formation of Bohu Depression, including alluvial fan, braided river delta plain, delta front, shore-shallowlacustrine, turbidite fan and semideep lake facies. Meanwhile, there developed five types of larger sedimentary bodies, which corresponds to the three provinces in the northwest, northeast and south of the study area. It is considered that lithologic traps are less developed in the lower segment ofSangonghe Formation, only formed in the locally developed mouth bar, shore-shallowlacustrine beach bar and turbidite fan.

Extensional folds and their control effect on oil and gas accumulation:A case study from Beizhong sub-depression in Hailar Basin

ZHANG Ying

2012, Vol.24(2): 16–20 Abstract ( 504 ) PDF (753 KB) ( 816 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.004

Beizhong sub-depression is one of the richest oil and gas tectonic units in the Hailar Basin, and it experienced three stages, including rift period, rift-depression period and depression period, which shaped a current complex structure. The west fault-step belt, the east fault-step belt and the lowuplift belt of subsag comprised a typical longitudinal isostatic extensional fold. The actions of extensional stress and gravity created secondary structural styles in the extensional fold, such as tilted faulted-block and slide faulted-ramp. Extensional folds provide important structure of oilgas for extensional basins. The favorable traps and sedimentary facies related to extensional folds can accelerate the accumulation of oil and gas. Extensional folds play an important role in controlling oil and gas accumulation in Beizhong sub-depression. Its role mainly embodies two respects: the center lowuplift belt is a multiple oil and gas accumulation zone; while the slide faulted-ramp near boundary faults is favorable for oil and gas accumulation.

Diagenesis of Paleogene-Neogene sandstone reservoirs in Lenghu-Maxian area, northern Qaidam Basin

CHEN Ji， ZHANG Yongmei， SHI Ji’an， ZHANG Yongshu， SUN Guoqiang， WANG Guocang

2012, Vol.24(2): 21–25 Abstract ( 470 ) PDF (449 KB) ( 635 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.005

Based on cores, cast thin sections, scanning electron microscope and testing data, this paper studied the diagenesis of Paleogene-Neogene sandstone reservoirs and its influence on reservoir properties in Lenghu-Maxian area in north QaidamBasin. The result shows that the sandstone reservoirs in this area are mainly composed of lithic arkose, arkose and feldspar lithic sandstone, and mainly experienced such actions as compaction, cementation and dissolution. Mechanical compaction is the main compaction, cementations are mainly carbonate cementation, sulfate cementation, quartz overgrowth and clayminerals cementation, and dissolution comprises carbonate cementation content and detrital dissolution. Compaction and cementation caused the destruction of primary pores and made the reservoir properties poor. Dissolution of the lithic and cement was the main reason for generating secondary pores. According to the characteristics of vitrinite reflectance and clay minerals, it is ascertained that the evolution have reached the early diagenetic stage A, and the minor part reached the middle diagenetic stage B.

Effect of clay minerals on low resistivity of Chang 61 reservoir in Wuqi area

ZHOU Kang，LIU Jiaqing，DUAN Guoying，DING Lei,ZHOU Lindan

2012, Vol.24(2): 26–30 Abstract ( 482 ) PDF (485 KB) ( 655 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.006

In order to understand the effect of clayminerals on lowresistivity reservoirs, the slice, scanning electronic microscope, X-ray diffraction, logging interpretation and oil testing results were applied to study the effect of clay minerals on resistivity of Chang 61 reservoir in Wuqi area. The result shows that clay minerals play a dominate role on the forming of low resistivity reservoir. The role displays in the following three aspects: the role mainly is additional conductivity, and it is strongest in the illite/smectite mixed layer and is the key factor for resistivity decline; followed by the pore structure reformation which caused the bound water saturation increasing and resistivity decline, and it is most in illite; and then the absorption of water molecule which is mainly in chlorite. By considering the effects and mineral content, it was believed that the order of effect of clay minerals on resistivity is: illite > illite/semectite mixed layer > chlorite > kaolinite. This study result can be used to interpret the mechanism and predict the distribution of low resistivity reservoir.

Characteristics and evaluation of carbonate reservoir in the southern Qilian Basin

ZHAO Junhui, ZHOU Lifa

2012, Vol.24(2): 31–36 Abstract ( 460 ) PDF (637 KB) ( 529 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.007

Based on the analysis of rock thin section, scanning electron microscope and properties, the characteristics of the carbonate reservoir in the southern Qilian Basin were studied. The result shows that reservoir rocks are dominated by oolith limestone, bioclastic limestone, micrite limestone and little dolomite, and the best oolith limestone reservoir mainly developed within Middle Triassic Dajialian Formation. The reservoir space is mainly secondary pores developed in intragranular dissolved pores, intergranular dissolved pores, intercrystal dissolved pores and fractures. The reservoir properties are poor, with ultra-lowporosity and lowpermeability. Dolomitization, dissolution and tectonism improve the reservoir properties, while cementation and compaction play destructive roles to reservoir properties and pores of reservoir, which results in poor porosity and permeability. According to reservoir properties and pore structure parameters, the reservoirs in the study area are divided into type Ⅲ and type Ⅳ.

Study on volcanic reservoir types in Subei exploration area

ZUO Guoping， TU Xiaolong， XIA Jiufeng

2012, Vol.24(2): 37–41 Abstract ( 455 ) PDF (558 KB) ( 530 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.008

Being widely developed in Subei exploration area, volcanic rocks are characterized by fast lateral and vertical change, complicated accumulation rule, which causes great difficulties for oil and gas exploration. By analyzing source rocks, matching characteristics of reservoir and cap rock, combining with seismic data, this paper studied the contact relationship of volcanic and source rocks, and studied the volcanic reservoir accumulation model. There are six types of reservoir accumulation model, including indirect contact of source rocks and volcanic rocks, direct contact of source rocks and volcanic rocks, volcanic rocks enwrapped by the source rocks, source rocks developed on and below the volcanic rocks, volcanic reservoir developed on the top of volcanic conduit and volcanic rocks acted as seal. These reservoir accumulation models were used to predict the volcanic reservoir at the Funing and Sanduo formations in Eogene. Totally, they can be summed up to three types of volcanic reservoir, including the relationship of source and reservoir represents as enwrapping（near source rocks）, the relationship of source and reservoir shows as up and down （near source rocks）, and faults act as the main hydrocarbon migration path.

Fracture features description of Xujiahe Formation in Puguang area, northeastern Sichuan Basin

TANG Qunying， YIN Taiju， LU Yao， CAIWen，WU Jun， REN Qiangyan

2012, Vol.24(2): 42–47 Abstract ( 525 ) PDF (637 KB) ( 694 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.009

As the main target layer of terrestrial formation in Puguang area, Xujiahe Formation is characterized by poor properties, low porosity and low permeability. Based on core description, slice observation, EMI imaging logging, this paper carried out fine description and study on fractures of Xujiahe Formation in Pulu 1 well, discussed the types, characteristics and distribution rules of fractures, and analyzed its influence on reservoir properties and production capacity. The result shows that fractures developed in Xujiahe Formation in the study area are almost structural with high angles and non-structured with low angles, which have a high degree to be filled by carbon and calcite, and fractures highly developed but unevenly distributed in the second, fourth and sixth member of Xujiahe Formatrion in vertical. It is considered that fractures not only become reservoir spaces of fluid, but also be the flowing channels of fluid, which plays an important role in improving reservoir properties.

Characteristics of calcite cements of Chang 6 oil reservoir set in Huaqing area

ZHANG Yingying， HUANG Sijing

2012, Vol.24(2): 48–52 Abstract ( 401 ) PDF (524 KB) ( 664 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.010

The Triassic Chang 6 oil reservoir set in Huaqing area is the main hydrocarbon reservoir and producing formation of Mesozoic in Ordao Basin. The cementation of calcite cements is a major factor for the tight reservoir. The analyses on thin section, cathodoluminescence, elemental composition and carbon isotope show that most of the calcites cemented in granular and poecilitic texture, and a fewcemented in micrite texture which are the matrix of syndepositional lake facies. There are several different genetic mechanisms for the granular and poecilitic calcite cements formed during post sedimentary stages, and the calcite cements deposited during the early diagenetic A stage are in connection with the hydration of aluminumsilicateminerals, metamorphic rocks and magmatic rocks. The ferrocalcite cements filled not only in the primary pore, but also in secondary pores. The formation of ferrocalcite cements are closely related to the aluminum silicate minerals and the transformation of clay mineral and occurred during the early diagenetic B stage. Themost cementation of the calcites and ferrocalcite are disadvantageous for the reservoir properties.

Response relation between volcanic lithofacies and seismic facies and its application: A case study from Haerjiawu Formation in Malang Sag, Santanghu Basin

SI Xueqiang， CHEN Wei， YANG Zhili， WANG Xin， SANG Tingyi， WEN Chuanjiang

2012, Vol.24(2): 53–60 Abstract ( 523 ) PDF (1185 KB) ( 775 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.011

In order to study the distribution characteristics and define the exploration direction of volcanic reservoirs of Haerjiawu Formation in Malang Sag of Santanghu Basin, it is necessary to establish the response relation between volcanic lithofacies and seismic facies, and carry out the identification and prediction of volcanic rocks. The cores and casting thin sections were used to define the lithologies and lithofacies characteristics of volcanic rocks. Combined detailed logging-seismic calibration and seismic response characteristics, this paper summarized the response relation between volcanic lithofacies and seismic facies, and then predicted the volcanic reservoirs. The study result shows that overflow facies and volcanic sedimentary facies are the main lithofacies of Haerjiawu Formation, and the seismic reflection characteristics mainly are weak swing and blank lenticular pattern, middle-weak swing and weakly continuous moundy pattern, middle-strong swing and moderate continuous lamellar phase. According to the prediction, it is considered that the volcanic rocks of Haerjiawu Formation has the characteristics of central type eruption, there are mostly layered volcanos or konides, and subaerial eruption and subaquatic eruption both can be found in the sag. The distributed area ofmandelstone in mid-range crater is favorable for oil-gas exploration.

Discussion on oil sources and petroleum migration in the Wunan Oilfield, Qaidam Basin

ZHANGMingfeng， TUO Jincai， ZHANG Xiaojun，WU Chenjun， GUO Lijun

2012, Vol.24(2): 61–66 Abstract ( 520 ) PDF (693 KB) ( 710 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.012

The geochemical features of the crude oil samples collected from the Wunan Oilfield in southwestern margin of Qaidam Basin were analyzed. The result shows that the n-alkanes presented a bimodal distribution pattern （odd-toeven and even-to-odd carbon predominance）, with the low ratios for both Pr/Ph（< 0.5） and C35 -Hopane/C34 -Hopane （< 1.0）, and high contents of tricyclic-terpanes and gammacerane, which indicates that the crude oil formed in a midsalty to salty water reduction depositional environment, and the parent material are mainly from the lower aquatic organisms.Moreover,maturity parameters of hopane and sterane reflect its lowmaturity of crude oil. According to the oilsource correlation, the crude oil derived from the Xiaganchaigou Formation （E32） of Zhaha-Qiekelike depression. The type of crude oil is more consistent from the same source, thus the significant oil-migration effects of nitrogen compounds in the oil are observed. The composition and relative abundance of nitrogen compounds in the crude oil were used to discuss the petroleum migration in the Wunan oilfield. With the increasing of the migration distance, the concentration of nitrogen compounds is decreased, which indicates that crude oil generated on its west adjacent depression, and migrated fromwest to north and fromnorthwest to southeast. It is concluded that the crude oil in the study area came fromthe western Zhaha-Qiekelike depression.

Division of sedimentary cycle sequences based on maximum entropy spectrum estimation

ZHU Jianbing

2012, Vol.24(2): 67–71 Abstract ( 356 ) PDF (535 KB) ( 597 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.013

In order to improve the division accuracy of sedimentary cycles by log, this paper estimated the prediction error of well log data by using maximum entropy spectrum estimation, and then obtained the prediction error trend curve. Symmetric and asymmetric models were applied to verify this method. The result shows that prediction error curve can be used to identify sedimentary cyclic interface well, and prediction error trend curve can be used to identify half cyclic sequences. This method was applied to divide the cyclic sequences of real well log data, and good results have been obtained.

Characteristics and significance of petrology of Changxing Formation in Yuanba area, northeastern Sichuan

WU Qilin， FU Heng， LI Xiuhua， HAN Dingkun， HUANG Yong， DUAN Jinbao

2012, Vol.24(2): 72–76 Abstract ( 459 ) PDF (502 KB) ( 559 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.014

Based on thin section collection and microscope observation by six wells of Changxing Formation in Yuanba area, 30 types of rocks and four types of sediment sources were identified. Radiolarian chert was identified firstly in this area，which is the evidence of the existence of deep-sea sedimentary environment in early Changxing Formation.

Characteristics and controlling factors of calcarenaceous sandstone reservoir in the middle part of western Sichuan Basin

LIU Huan， PENG Jun， LI Lijuan， LUO Wenjun， XIAO Yan

2012, Vol.24(2): 77–82 Abstract ( 424 ) PDF (563 KB) ( 610 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.015

The calcarenaceous sandstone in Fenggu-Hexingchang area is typical tight sandstone reservoir. In order to find out the reasons, this paper studied the reservoir characteristics and the influencing factors of physical properties based on analyses of cores, slice and test data. The result shows that the calcarenaceous sandstone reservoir has high contents of carbonate debris, with medium-well sorting, medium psephicity, point-line contact forms and pore-contact cementation among rock grains. The calcarenaceous sandstone reservoir belongs to the lowporosity and lowpermeability reservoirs, and secondary pores are the main reservoir spaces. The reservoir properties are affected by deposition and diagenesis. The deposition dominated the reservoir properties on the macro and underwater distributary channel is the main favorable microfacie. Furthermore，the strong compaction and cementation are the main factors resulting in the low porosity and low permeability of the reservoir, while kaolinite is the main clay mineral，which has constructive effect on keeping the pore space of reservoir. The dissolution is the main factor improving the reservoir properties.

Derivation of new material balance equation for adsorbed gas reservoir and reserve estimation

WANG Delong， GUO Ping， CHEN Heng， FU Weifeng， WANG Zhongde， DING Hongkun

2012, Vol.24(2): 83–86 Abstract ( 526 ) PDF (314 KB) ( 609 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.016

During the exploitation process of unconventional adsorbed gas reservoirs, as formation pressure decreases, adsorbed gas will be desorbed and make adsorbed layer decrease and free gas space increase. At present, the material balance equation considering adsorbed layer volume variation has not been established and has not been applied to research the influence of adsorbed layer volume variation and density on adsorbed gas reservoir reserves. This paper firstly established newmaterial balance equation considering the adsorbed layer volume variation. The application cases proved the applicability and reliability of this equation, and it is cognized that adsorbed layer volume variation and density have greater influence on natural gas reserves estimation.

Key technologies of 3D seismic data multi-survey joint processing and its application effect analysis in Songliao Basin

CHEN Keyang， WU Qingling， LI Lailin， FAN Xingcai， GUAN Xin， BI Min

2012, Vol.24(2): 87–91 Abstract ( 414 ) PDF (777 KB) ( 607 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.017

To solve the general problems such as uneven energy, inconsistent wavelet and empty binning of the 3D seismic data among the multi-survey joint processing blocks, methods of energy optimized adjustment method based on fold coverage, cross correlation time shift computation and adjustment method among the blocks, residual static method after surface consistent predictive deconvolution and post-stack time migration after post-stack interpolation were applied to ensure the consistence of amplitude energy and wavelet characteristics among the blocks with no joint time shift. The result shows that the proposed key technologies can obviously improve the processing quality in both shallow and deep parts, and there is no spatial spurious frequency of the migration section with high signal to noise ratio.

Applying duplex wave migration technology to predict faults and fractures in reef limestone reservoir

LI Bin，LUO Donghong，LIANG Wei，WANG Ruiliang，WANG Su，DAI Jianwen

2012, Vol.24(2): 92–97 Abstract ( 426 ) PDF (766 KB) ( 371 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.018

Due to lowresolution seismic data and complex inner structure ofAoilfield in South China Sea, it is difficult to predict the faults and fractures. This paper adopted duplex wave migration（DWM） technology to predict the faults and fractures in this oilfield. Based on 3D seismic shot gather information and pre-stack depth migration velocity model in depth domain, combined with DWMvelocity scan and migration aperture analysis, DWMtechnology was used to refine the velocitymodel further, then obtained the 3D data of fault and fractures imaging. According to the DWMdata and its explaining results, depth migration data and its attributions, such as coherence cube, dip and amplitude and so on, structure explaining results by normal seismic explanation, drilling and logging data, the characteristics and distribution law of the faults and fractures of the oilfield were recognized. It is proved that the DWMtechnology can be used to not only predict the fault and fracture system, which can be predicted by normal seismic, but also predict those unpredictable fault, fracture, and lithologic interface.

Calculation of original gas in place and water influx in the Sebei Gas Field, Qaidam Basin

DENG Chenggang，SUN Yong，CAO Jihua，HE Yan

2012, Vol.24(2): 98–101 Abstract ( 480 ) PDF (263 KB) ( 474 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.019

Original gas in place（OGIP） and water influx are the key parameters to determinate development strategy and production scheme for a gas reservoir. Traditional apparent formation pressure is common process for judging gas reservoir drive mechanism. However for those gas reservoirs weakly affected bywater drive, its pressure drop curve is a straight line in early period, easily to be misinterpreted as elastic energy driving, and its OGIP calculation results are also greater than using geologic reserve calculation method with water drive. TakingA gas reservoir in Sebei No. 2 gas field as an example, this paper applied apparent geologic reserves method under the situation of unknown water influx to estimate OGIP from mapping apparent geological reserve curves, and then backward calculated water influx by putting OGIP data into the equation. This calculation method is proved to be an effective approach for Sebei Gas Filed. Simultaneously, it also has positivemeaning to guiding the gas field development during the later period.

Study on optimal well completion based on fuzzy comprehensive evaluation model

ZHAO Xiaolong， LIU Xiangjun， LIANG Lixi， YANG Chao， CHEN Chunyu， LIU Daojie

2012, Vol.24(2): 102–105 Abstract ( 367 ) PDF (276 KB) ( 537 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.020

The uncertainties, randomness and fuzziness exist in many factors such as output，net present value，completion cost，deliverability, edge and bottom water coning and the degree of the reservoir rock soundness and so on, which all influence the selection ofwell completion. By adopting relative deviation fuzzymatrix, fuzzy analytic hierarchy process and fuzzymatrix synthesis operator, this paper improved fuzzy comprehensive evaluation model. In this model, we generalized the influencing factors, weighed the technology index and economy index, comprehensively evaluated the well completion system, and worked out the optimal membership degree. The improved model evaluation result agreed more with the reality, which proves the feasibility, superiority and reliability of this improved fuzzy comprehensive evaluation model.

Research advance and prospect of low salinity water flooding

WANG Ping，JIANG Ruizhong，WANG Gongchang， LIANG Yu

2012, Vol.24(2): 106–110 Abstract ( 775 ) PDF (290 KB) ( 1713 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.021

Aiming at the current status that low salinity water flooding has been applied to pilot test abroad while in China there is little research, this paper analyzed the current research status and existing problems, and proposed prospects for low salinity water flooding. It is concluded that for sand reservoirs, the main mechanisms of low salinity water flooding are similar to alkaline flooding, fines migration and the wettability alteration caused bymulti-component ion exchange, while for carbonate reservoirs, the mechanismof lowsalinitywater flooding is wettability alteration caused bymulti-component ion exchange. Crude oil properties, reservoir rock properties, formation and injected water salinity and reservoir temperature can all influence the effects of low salinity water flooding. The main problems lie in the unclear mechanisms, low salinity water source limitation and reservoir adaptability. Finally, it is pointed out that low salinity water flooding can be combined with current oilfield development techniques, coal bed methane production techniques, development techniques for low permeability oilfield and high water-cut oilfield, which will form new economical, environmental-friendly and great potential techniques for enhanced oil recovery.

Reservoir heterogeneity and its relation with remaining oil distribution in the Matouzhuang Oilfield

LIU Wenchao

2012, Vol.24(2): 111–116 Abstract ( 427 ) PDF (417 KB) ( 541 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.022

Taking Zhuang-2 fault block of the Matouzhuang Oilfield as an example, this paper computed heterogeneous synthetic index by means of entropy weight algorithm to characterize the reservoir heterogeneity, applied the synthetic index to establish heterogeneous model, analyzed the internal, interlayer, plane and space heterogeneity, and discussed the relationship between the heterogeneity and remaining oil. The result shows that there are great differences of heterogeneity among the sublayers. The heterogeneity is weak in shore-shallowlacustrine mixing beach, strong in subaqueous interdistributary bay, middle to weak in subaqueous distributary channel and mouth bar, and strong in front sand sheet. The interlayer heterogeneity is middle to strong. The heterogeneity in plane presents middle degree. Reservoir heterogeneity is affected by sedimentary microfacies, diagenesis and long-term waterflood. Remaining oil mainly distributed in the area where herterogeneity is weak.

Heterogeneity of sandy conglomerate reservoir and its influence on remaining oil distribution: A case study from Badaowan Formation in the mid-west of block Ⅱ in Karamay Oilfield

HE Hui， SONG Xinmin， JIANG Youwei， PENG Shimi， LI Yanlan， SUN Jingmin

2012, Vol.24(2): 117–123 Abstract ( 513 ) PDF (706 KB) ( 669 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.023

At present, the voidage-injection imbalance, interlayer interference and in-layer interference leaded by the reservoir heterogeneity are extremely highlighted during the production tail of sandy conglomerate reservoir in the midfan of alluvial fan. Taking the Jurassic Badaowan Formation in mid-west of the block II in Karamay Oilfield as an example, this paper studied the reservoir heterogeneity of alluvial fan sandy conglomerate reservoir. Based on outcrop observation, core description, electrofacies analysis, the single sand body description technique was used to divide the reservoir into 4 types of microfacies-lithofacies single sand body. Combining with the macroscopic and microscopic heterogeneity in different single sand body, the remaining oil were divided into 3 enriched types: Ⅰ-type braided channel gritstone facies, which has mesopore and small throat texture; Ⅱ-type braided channel fine sandstone facies, which has small pore and small throat texture; Ⅲ-type braided channel sandy conglomerate facies, which has small pore and fine throat texture. It is concluded that the type Ⅲ has the best water flooding effect and should be the main object of stabilizing oil production and controllingwater cut, and the type I and Ⅱ , where the properties are relativelyworse and the heterogeneity is stronger, should be the next potential target. Using this method of “recognizing the reservoir heterogeneity and resolving it” as the breakthrough point to analyze the single sand body and the heterogeneity, which can provide better reference for forecasting the distribution of remaining oil in the sandy conglomerate reservoir.

Pressure curve characteristics for wells drilled in cave of fracture-cavity carbonate reservoirs

LIU Hong， REN Lu， HU Zhihua

2012, Vol.24(2): 124–128 Abstract ( 403 ) PDF (400 KB) ( 617 )

doi: https://doi.org/10.3969/j.issn.1673-8926.2012.02.024

Drilling stem emptying, massive mud leakage and acidification transformation appeared during the drilling process of fracture-cavity reservoirs, which increased difficulties for reservoir well test interpretation if using triple porosity well test method. It has great actual significance to establish well test interpretation model for wells drilled in cave and carry out well test interpretation of this reservoir. Based on the double porositymodel, taking inner cave as an equipotential body whose internal pressure was equal everywhere, making outer fluid flow observe Darcy law, and according to cave mass conservation equation, a new well test interpretation model for wells drilled in cave was presented. Laplace transform and Stehfest reverse method were used to solve the model. The influences of cave storage ratio, size of cave, matrix interporosity flowcoefficient and fracture storage ratio on the bottom pressure were analyzed. And the double log curve for wells drilled in cave of fracture-cavity carbonate reservoirs was used to interpret the measured pressure of some well in TZ area. Good results have been obtained, and this research can provide theory guidance for fracture-cavity reservoirs well test interpretation.