石油实验地质

2017, 39(5): .

Abstract(275) PDF-CN(240)

Abstract:

Depression and apophysis structure type and its controls on deposition in the Jiyang Depression, Bohai Bay Basin

Xu Chunhua, Wang Yalin

2017, 39(5): 587-592. doi: 10.11781/sysydz201705587

Abstract(1168) PDF-CN(499)

Abstract:
Glutenite oil deposits in steep slope zone are major hydrocarbon exploration targets in rift basins. Drilling proves that near-source coarse debris sediments were well developed on the downthrown side of EW oriented faults. On the contrary, near-source sediments seldom or even did not develop on the downthrown side of N(N)E oriented faults. The article discussed the coupling relationship between bulge and depression, and came up with two kinds of coupling relationship which are the mountain-upheaval basin-sedimentary type and basin-sedimentary mountain-upheaval type, focusing on this special phenomenon and based on the recovery of the denudation quantity in the bulge area. Provenance area, erosion thickness and passageway development degree determined whether near-source sediments deposited or not based on the studies of the Dabie orogenic belt. The deposition characteristics of the downthrown side of the EW and N(N)E oriented faults were analyzed, indicating that the EW faults are syndepositional ones and the N(N)E faults are right-lateral strike-slip ones influenced by the SN extensive stress during Paleogene. The difference between kinematic properties and activity time is the main cause of sedimentation difference.

Sequence stratigraphy and sedimentary evolution from the 4th member of Quantou Formation to the 3rd member of Nenjiang Formation in Sifangtuozi area, Songliao Basin

Fan Qi, Fan Tailiang, Tian Jijun, Sun Minghe, Li Shu

2017, 39(5): 593-602. doi: 10.11781/sysydz201705593

Abstract(922) PDF-CN(266)

Abstract:
The sequence stratigraphy and sedimentary evolution from the 4th member of Quantou Formation to the 3rd member of Nenjiang Formation in Sifangtuozi area of the Songliao Basin were studied based on data collected from 147 exploration wells, 300 development wells and 25 cored wells. Research shows that by analyzing petrology, sedimentary structures and seismic inversions, the targeted strata can be classified into three second order sequences, seven third order sequences and twenty-one fourth order sequences. Under the sequence framework, meandering river deltas and shallow lakes were developed when the 4th member of Quantou Formation was deposited, and braided river deltas, shallow, semi-deep and deep lakes were developed when the Qingshankou and Nenjiang formations were deposited. In this process, the changing of base level, the left-lateral slip of Yanshan Movement and the transgression jointly contributed to the results, including the provenance changing from Baicheng to Yingtai, and then to Nehe drainages. In addition, the depocenter migrated from the Qijia Sag to the Sanzhao Sag, which highlighted the deltaic cycle in a direction of SW-NW-NE and the occurrences of maximum flooding surfaces in the 1st member of Qingshankou Formation and the 2nd member of Nenjiang Formation. We recommend looking for oil and gas on low-scoped ridges and shale resources on MFSs.

Hydrocarbon accumulation in Sanhecun Sag,Jiyang Depression,Bohai Bay Basin

Meng Tao, Qiu Longwei, Wang Yongshi, Liu Yali, Liu Peng, Cheng Fuqi

2017, 39(5): 603-609. doi: 10.11781/sysydz201705603

Abstract(1077) PDF-CN(230)

Abstract:
The migrated oil and gas from the Bonan Sag accumulating in the Sanhecun Sag of Bonan Depression of Bohai Bay Basin was studied using fluid inclusion and biomarker compound analyses, combined with the burial history modelling of typical wells and the evolution history of boundary faults. A new understanding was proposed from two aspects including oil and gas accumulation time and migration path evolution. Three hydrocarbon accumulation processes occurred in the Sanhecun Sag during the early Dongying, Guantao and late Minghuazhen periods according to fluid inclusion homogenization temperatures and biomarkers which reflect maturity.The early oil and gas mainly derived from the upper part of the fourth member of Shahejie Formation, and then from the third and first members of Shahejie Formation in the Bonan Sag, forming a complete hydrocarbon accumulation sequence in the Sanhecun area. During the accumulation period of Dongying Formation, boundary faults failed to stagger delta sand body. As a result, the Bonan oil and gas directly migrated along the contiguous sand and accumulated in Sanhecun area. Faults, sand bodies and unconformities provided a good migration channel for late oil and gas migration.It is confirmed that oil and gas migrated through "the early unified sand body" and "fault-sand body-unconformity composite" to Sanhecun Sag and the southern slope and then accumulated, forming a variety of oil and gas accumulation types.

Reservoir characteristics and main controlling factors of the Cambrian Xixiangchi Formation in the Sichuan Basin

Lin Yi, Chen Cong, Shan Shujiao, Zeng Yiyang, Liu Xin, Chen Youlian

2017, 39(5): 610-617. doi: 10.11781/sysydz201705610

Abstract(1133) PDF-CN(388)

Abstract:
The middle and lower Cambrian Xixiangchi Formation in the Sichuan Basin is a gas-bearing formation with a good potential. Its exploration degree is still very low at present, and the reservoir characteristics and main controls are not clear. Core, thin section and testing data were integrated to study the rock types, reservoir space, physical properties and controlling factors of the Xixiangchi reservoirs. The Xixiangchi reservoirs are mainly grain dolomites, followed by aplite-dolomites. The reservoir space includes pores, caves and fractures, and the reservoir type is fracture-pore type. The physical properties of the reservoirs are characterized by low porosity and low permeability, and locally high porosity and high permeability, showing a strong heterogeneity. For the distribution, the Xixiangchi reservoirs vertically stacked and have a poor lateral continuity. Thick reservoirs appear from the central Sichuan Basin to well GT 2 in the east, and then thinned in Wubaiti area. In Fengjie and Xishui areas at the basin edge, reservoirs distribute as belts, and are thinner compared to those in the basin center. Reservoir development was controlled by sedimentary facies obviously. In the grain shoal area, reservoirs have a high development degree. Besides, constructive diagenesis and tectonic fracture have positive effects on reservoir development.

Multiple scale fluctuations of the Early Triassic sea level and its influence on reservoirs in the Sichuan Basin

Xiao Jiaojing, Wang Longzhang, Chen Mei, Chen Zhibin, Zhou Jie, Chen Peng

2017, 39(5): 618-624. doi: 10.11781/sysydz201705618

Abstract(869) PDF-CN(210)

Abstract:
Multiple scale sequences of carbonate oolitic bank developed in Jichang profile of the northeastern Sichuan Basin in the Early Triassic. Several isotopic and elemental proxies were used to reveal the sea-level fluctuation when those sequences formed. The changes of carbon and oxygen isotopes, which are coincident with the high frequency sea level fluctuation, could be used for stratigraphic sequence division. δ¹³C increasing and δ¹⁸O decreasing are used as the proxies of sea level rising, showed in regressive parasequence sets. δ¹³C decreasing and δ¹⁸O increasing are used as the proxies of sea level falling, detected from trangressive parasequence sets. Five parasequence sets, named as pss1-pss5, were distinguished from the first and second members of the Feixianguan Formation from where we sampled. 5 fifth order cycles of sea level fluctuation were recognized and grouped into 2 forth order cycles of sea level fluctuation. The Sr and Mn contents indicate the low frequency fluctuation of sea level, indicating the background of sedimentary and diagenetic environment. The increasing contents of Sr isotope are coincide with the long-term fluctuation of global sea level. Mn contents are related to water depth, enriching in deep water and poor in shallow littoral water. The Sr, Mn content changes indicate the long-term trend of the sea level fluctuation.

New understanding of oil and gas geological characteristics and resource potential in Wan'an Basin

Zhang Houhe, He Shuanzhu, Liu Peng, Liao Zongbao, Xu Qingmei, Zhu Xiaomin, Xu Yaohui

2017, 39(5): 625-632. doi: 10.11781/sysydz201705625

Abstract(1547) PDF-CN(231)

Abstract:
The geological conditions, hydrocarbon distribution and enrichment regularity in the Wan'an Basin were systematically analyzed based on the latest seismic and test data. Some new understanding of oil and gas geological characteristics and resource potential were obtained. The Wan'an Basin experienced two tectonic evolution stages: fault depression phase and depression phase. Inshore limnetic, shore delta, fan delta, coastal-shallow sea, and bathyal facies deposited. Sediments are from west to east. The major source rocks are mudstone, shale, coal and coal-bearing mudstone in the Oligocene and Miocene, which mainly distributed in the central and northern depressions. There are three kinds of reservoirs, respectively the sandstones of Oligocene to Pliocene, the carbonate rocks of Middle to Upper Miocene, and the bed rocks of pre-Tertiary. There are two sets of regional cap rocks, the Pliocene-Quaternary and the Upper Oligocene-Lower Miocene. There are three favorable oil-and-gas regions, the west, the central and the southern zones. Oil and gas potential of the Wan'an Basin is tremendous, and the geology resources of oil and gas are 29.38×10⁸ t and 34 897×10⁸ m³, respectively.

Differences of sedimentary characteristics of sublacustrine fans between conglomerate-rich and sand-rich types in the Weixinan Sag, Beibu Gulf Basin

Zhang Hui, Zeng Xiaoming, Huang Dongmei, Chen Xiaowu, Mo Fengyang, Wu Bibo

2017, 39(5): 633-639. doi: 10.11781/sysydz201705633

Abstract(796) PDF-CN(211)

Abstract:
Large oil and gas resources have been found in sublacustrine fans of the 1st member of Liushagang Formation in the Weixinan Sag, Beibu Gulf Basin. The sublacustrine fans in the study area were divided into conglomerate-rich and sand-rich types through the analyses of assay, core, logging and seismic data in order to clarify the reasons for different development effects of sublacustrine fans in different fields. The main reasons for different sedimentary characteristics include ancient landforms and provenance supply. Two kinds of sedimentary models of sublacustrine fans were summarized. Gravity slumping was the main trigger mechanism for sand-rich sublacustrine fans while tectonic movement was the main trigger mechanism for conglomerate-rich sublacustrine fans. Both had a good source-reservoir-caprock assemblage. However, due to poor physical properties, the favorable exploration direction for conglomerate-rich sublacustrine fans was to find secondary porosity development zones. Sand-rich sublacustrine fans were suitable to host effective traps due to better physical properties.

Hydrocarbon accumulation model and controlling factors in the Upper Paleozoic in Jurong area, Lower Yangtze region

Wang Dongyan, Peng Jinning, Qiu Qi, Lü Junxiang

2017, 39(5): 640-646. doi: 10.11781/sysydz201705640

Abstract(803) PDF-CN(161)

Abstract:
The main controlling factors of a hydrocarbon accumulation model of the upper Paleozoic in the Jurong area of the Lower Yangtze region were discussed. Regional geology and hydrocarbon accumulation processes in some key exploration wells were studied using the relationship between oil and gas accumulation elements and the spatial-temporal distribution of the marine strata in the Upper Paleozoic in the study area. The results showed that: (1) The Upper Paleozoic Longtan and Qinglong formations provided source rocks, carbonate fractures on the Indosinian unconformity surface and the tight sandstones in the Longtan Formation worked as reservoirs, and the shale in the Gecun and Pukou formations functioned as cap rocks. The tectonic and accumulation histories obtained from typical exploration wells indicated that traps were formed and adjusted continuously due to multiple tectonic activities. The tectonic uplift during the late Himalayan period destroyed hydrocarbon reservoirs, leading to a great loss of oil and gas in Jurong area. (2) Three classes of oil and gas reservoirs developed, including the secondary residual, primary preservation and the late reconstruction types. Preservation conditions for oil and gas were the key factors for hydrocarbon accumulation in Jurong area. The Qinglong Formation experienced erosion and leaching during the Indosinian and Yanshanian periods, forming a large number of caves and cracks, which controlled the late reconstruction of fractured-vuggy carbonate reservoirs on the unconformity surface.

Classification and evaluation of micro pore structure of volcanic rock reservoirs: A case study of the Carboniferous volcanic reservoirs in Xiquan area, eastern Junggar Basin

Ma Shangwei, Luo Jinglan, Chen Chunyong, He Xianying, Dai Jingjing, Xu Xuelong, Wang Chong

2017, 39(5): 647-654. doi: 10.11781/sysydz201705647

Abstract(1142) PDF-CN(200)

Abstract:
The studies of the characteristics of volcanic reservoirs in Xiquan area of the Junggar Basin are relatively weak. The pore types and pore assemblages as well as the micro pore structural features of the Carboniferous volcanic reservoirs in Xiquan area were classified and evaluated in this paper according to hydrocarbon yield, and also based on the observation and description of cores from 25 drilling wells, and the identification and quantifying of casting thin sections under microscope, measurement of SEM, porosity and permeability and capillary pressure. Four types of volcanic reservoirs were identified based on the thin-section porosity and the superior pore assemblage. The type Ⅰ pore assemblage is the vesicles+enlarged dissolution vesicles and dissolution pores+fractures. The type Ⅱ includes vesicles+structural fractures+dissolution fissures. The type Ⅲ is vesicles+dissolution pores, while only isolated fine pores developed in the type Ⅳ reservoir. The thin-section porosity reduces in turn from the type Ⅰ to the type Ⅳ. Different micropore structure of the volcanic reservoirs indicated that the type Ⅰ is an excellent reservoir with well-developed large pores and coarse throats. The type Ⅱ and type Ⅲ are better to medium favorable reservoirs with developed large to medium pores and medium to fine throats. While the type Ⅳ is a tight reservoir due to its fine pores and fine to micro throats. Finally, a volcanic reservoir classification and evaluation criterion for the study area was established on the basis of the above study and integrated with well logging data.

Characteristics and indications of rare earth elements in carbonates in the Buqu Formation, southern Qiangtang Basin

Wan Youli, Wang Jian, Wan Fang, Fu Xiugen, Wang Zhongwei, Shen Lijun

2017, 39(5): 655-665. doi: 10.11781/sysydz201705655

Abstract(880) PDF-CN(264)

Abstract:
The REE characteristics of different carbonate rock types were studied based on petrologic analyses of carbonate rocks from the Buqu Formation in ancient oil pools in the southern Qiangtang Basin. The carbonate rocks in the study area were classified into limestones, clay-dolomicrites, (residual) grain dolostones, crystalline dolo-stones and saddle dolomites. All kinds of carbonate rocks have a low REE content (∑REE), and some of the saddle dolomite samples have a higher ∑REE than limestones, indicating the mixing of outside liquids. Different carbonate rocks have different REE contents, but their distribution patterns are similar due to the standardization of surface waters of the Pacific Ocean. The La_N/Yb_N ratio averages 2.86, with a slight light rare earth concentration and a heavy rare earth loss. Light rare earth concentration degree decreases with the increase of dolomitization. The positive δCe anomaly (average 2.94) and positive δEu anomaly (average 1.43) showed that the Buqu carbonate rocks were deposited in an oxic environment. Dolomitization fluids mainly came from oceanic formation water in the same period. The diagenetic environment changed to reductive after hydrocarbon charging. At the end of Early Cretaceous, the Lhasa and Qiangtang blocks shear collided, helping atmospheric fresh water enter the Buqu Formation. Affected by the Cenozoic tectonic thermal event again, saddle dolomites were formed. Tectonic thermal events provided temperature conditions for Eu²⁺ concentration.

Geochemical characteristics and genetic model of rare earth elements in the Upper Cambrian dolomites in Gucheng area, Tarim Basin

Guo Chuntao, Li Dewu, Chen Shumin

2017, 39(5): 666-674. doi: 10.11781/sysydz201705666

Abstract(967) PDF-CN(176)

Abstract:
The special sedimentary and tectonic evolution in Gucheng area of the Tarim Basin indicated that dolomite formation might be unique. The REE geochemical characteristics of various kinds of crystalline dolomites and cave fillings were analyzed based on thin sections, cores and sedimentary environment analyses. The results showed that the NASC normalized REE distribution patterns of samples can be divided into four types: negative anomaly δCe and weak positive anomaly δEu, negative anomaly δEu, positive anomaly δEu, and positive anomaly δCe. Further studies showed that the main origin of dolomites was the evaporation pump model, and the hydrothermal environment was also important, while the influence of mixed water and burial dolomitization was relatively smaller. In addition, all the cave filling samples were formed in a mixed water and hydrothermal environment, while the evaporation pump and burial dolomitization did not form any filling samples, which might be helpful to find dolomite reservoirs.

Application of single hydrocarbon inclusions in petroleum geochemistry: A case study of the Tahe oilfield

Pan Anyang, Qin Jianzhong, Yao Suping, Tenger, Shen Baojian

2017, 39(5): 675-681. doi: 10.11781/sysydz201705675

Abstract(900) PDF-CN(209)

Abstract:
The hydrocarbon accumulation period and petroleum source characteristics in the Tahe oilfield were discussed using the newly developed methods for hydrocarbon inclusion analyses. The results confirmed that there were many stages of hydrocarbon accumulation in the Tahe oilfield, especially predominated by the Middle Hercynian and the Late Himalayan. The online laser ablation compositional analyses of single hydrocarbon inclusion showed that the early oil (yellow fluorescing inclusion) was characterized by bimodal n-alkane distribution and higher aromatic component content, belonging to medium crude oil with relatively lower maturity. In contrast, the late oil (blue fluorescing inclusion) was featured by unimodal n-alkane distribution and lower aromatic component content, belonging to late light crude oil at the middle-late mature stage. Based on the petroleum source or sedimentary environment of source rocks, hydrocarbon-forming organisms, maturity, migration distance, accumulation process and period, the early oil was suggested mainly from -C₁-O₁excellent source rocks and the late oil was mainly from O₃ carbonate source rocks.

Difference of methane adsorption capacity of kerogen and clay minerals

Guo Shaobin, Zhai Gangyi, Bao Shujing, Shi Dishi, Hu Jilin

2017, 39(5): 682-685. doi: 10.11781/sysydz201705682

Abstract(868) PDF-CN(309)

Abstract:
Shale gas mainly occurs in organic-rich shale in the form of free gas and adsorbed gas. At present, domestic and international research on the adsorption capacity of kerogen and clay minerals to methane is still relatively weak. A method for separating kerogen and clay minerals was proposed in this paper. The difference of adsorption capacity of methane in a unit mass of kerogen, illite mixed layer, kaolinite, chlorite and illite were studied by isothermal adsorption experiments on kerogen and different clay minerals. The experimental results indicated that the order of methane adsorption capacity is kerogen>illite mixed layer>kaolinite>chlorite>illite, and the gas adsorption capacity of kerogen in some samples is greater than the sum of that of clay minerals. The methane adsorption capacity of kerogen and clay single minerals decreases with temperature. At the same tempera-ture, the methane adsorption capacity of kerogen increases with vitrinite reflectance (R_o), while clay minerals are not affected by vitrinite reflectance.

Classification and evaluation of tight reservoirs in Fuyu oil layer, Sanzhao Sag, Songliao Basin

Lin Tiefeng, Kang Dejiang

2017, 39(5): 686-693. doi: 10.11781/sysydz201705686

Abstract(993) PDF-CN(160)

Abstract:
Fine evaluation is mainly embodied in two aspects: fine classification and vertical subdivision. The tight reservoirs in Fuyu oil layer can be divided into three categories, namely Ⅰ-1, Ⅰ-2 and Ⅱ combined with the study of sedimentary and sandbody characteristics, and by means of constant pressure mercury injection, high pressure mercury injection and nano microcosmic analysis. The boundary between tight oil reservoirs and conventional reservoirs is porosity 12%, permeability 1×10^-3 μm², pore throat radius 350 nm. The remaining Ⅰ-1 and Ⅰ-2 classes, as well as the Ⅰ-2 and Ⅱ standards, respectively, with the porosity of 10% and 8%, permeability of 0.25×10^-3 μm² and 0.1×10^-3 μm² as the boundary, corresponding to the pore throat radius of 150 nm and 75 nm. Each layer of the sand groups contains only 1-2 sand bodies based on the fine study of the longitudinal subdivision layer. Ⅰ class reservoirs mainly developed in FⅠ2-1, FⅠ3-1 and FⅡ2-2 sand groups. The remaining resources of different types of tight oil are implemented by layer, and through tight oil horizontal well drilling and large volume fracturing, tight oil resources can be explored effectively.

Shale gas reserve quality evaluation based on a comprehensive weighting method

Zhang Ling, Wei Shaolei, Huang Xuebing, Li Jun

2017, 39(5): 694-699. doi: 10.11781/sysydz201705694

Abstract(867) PDF-CN(153)

Abstract:
A shale gas reserve quality evaluation approach based on the comprehensive weighting method was proposed according to geological characteristics and special development processes. Some key factors which have great impacts on shale gas production were selected to build an evaluation system. A hierarchical analytical method was used to calculate the subjective weighting factors and a maximum entropy method was used to calculate the objective weighting factors. A comprehensive evaluation model was built based on subjective and objective weight-ing factors. A development risk factor was determined after analyzing the completion and match with existing reserves data. Grades with or without a risk factor can be provided simultaneously. With the proposed method, the quality of seven shale gas reserves was compared and their development order was determined according to the ranking for undeveloped reserves. The results indicated that many factors including geological, development and economic factors should be taken into consideration for shale gas reserve evaluation. Meanwhile, risk factors should be introduced as an evaluation factor. The evaluation results considering comprehensive relevant factors are reasonable and effective and can provide useful suggestions for future shale gas reserve management.

Pore structure characterization of tight oil reservoirs by a combined mercury method

Song Lei, Ning Zhengfu, Sun Yidan, Ding Guanyang, Du Huaming

2017, 39(5): 700-705. doi: 10.11781/sysydz201705700

Abstract(1312) PDF-CN(598)

Abstract:
Tight oil is an important component of unconventional oil and gas resources. The pore structure of tight oil reservoirs determines flow. In this paper, two kinds of mercury injection, pressure-controlled and rate-controlled, were used to carry out a quantitative characterization on eight tight core samples. The characteristics of pore structure characterization of the two methods were clarified one by one. The capillary pressure curves of eight samples were calculated on the same chart combining the two methods, and the pore size distribution histograms of eight samples were calculated according to Loucks classification method. The results show that: (1) At low mercury saturation, the total curve of rate-controlled mercury intrusion and the mercury injection curve of pressure-controlled mercury intrusion overlap well, indicating the same pore structure. (2) Pore size distribution curves show that the pore radius of tight oil reservoirs ranges 9.2 nm-500 μm with a multimodal pattern. There is a peak at 80-500 μm diameter, and the peak of the radius is about 150 μm. Nano pores with the pore radius of less than 1 μm developed well with multiple peaks. (3) According to Loucks' classification method, nano pores (<1 μm) are the main pore type, meso pores larger than 62.5 μm the second, and micron pores the least.

Technique and application of three-dimensional visualized information collection of full diameter oil and gas reservoir cores

Zhang Shoupeng, Fang Zhengwei, Yang Shidi, Mai Wen, Zhang Tongyao

2017, 39(5): 706-710. doi: 10.11781/sysydz201705706

Abstract(621) PDF-CN(295)

Abstract:
Geoscan series was established by means of X-ray intensity adjustment and scanning way update based on the micro X-ray computed tomography (CT). Sample room was converted to a flat type to extend scanning area, which realized the 3D scanning imaging of full diameter cores. Test results showed that the 3D parameters of full diameter, including core section structure, bedding structure, heterogeneous configuration and hole-seam distribution, could be used to get clear 3D images, which was difficult to describe in the past. Through the full diameter scanning of drilling cores, we analyzed the mineral content, hydrocarbon migration pathway and aperture ductility in a more extensive depth. The digital processing images of reservoir property parameters can reflect the effectiveness of hydrocarbon accumulation and the reservoir distribution rules. This technology provides a 3D visual image for the porosity and permeability of reservoir rocks and a qualitative evaluation of reservoir quality, which may optimize hydrocarbon explorations.

Differential deformation and its main controls on strike-slip structures: Evidence from sandbox experiments

Li Yanyou, Qi Jiafu, Zhou Shang

2017, 39(5): 711-715. doi: 10.11781/sysydz201705711

Abstract(990) PDF-CN(362)

Abstract:
Strike-slip faults and associated structures have major influences on hydrocarbon accumulation and exploration. Pre-existing structures and the competence of sedimentary strata lead to differential deformation features and spatial distribution of strike-slip fault systems. The differential deformation of basement-involved strike-slip faults and the influence of incompetent layers on overlying layers were investigated using physical sandbox experiments. The displacement of basement-involved strike-slip faults controlled the deformation style and intensity of overlying layers. Lithology and cap rock thickness controlled strike-slip range and deformation intensity in shallow formations. The width of a strike-slip zone increased with incompetent layer thickness. Physical sandbox experiments showed that with contraction of strike-slip displacement, which kind of structural styles were formed, fold or fault block, was determined by the thickness of incompetent layer. The change of strike on basement fault caused extension or contraction stress fields. It is an important factor to control the segmentation of strike-slip faults and the differential deformation of vertical tectonics.

Pore effect of dolomite reservoirs based on burial dissolution simulation: A case study of the Lower Cambrian Xiaoerbulake Formation in the Tarim Basin

Zheng Jianfeng, Shen Anjiang, Huang Lili, Chen Yongquan, She Min

2017, 39(5): 716-723. doi: 10.11781/sysydz201705716

Abstract(897) PDF-CN(209)

Abstract:
Burial dissolution is one of the important factors which control the development of dolomite reservoirs, but its effect on porosity is still not clear, which restricts the evaluation and exploration of burial dissolution dolomite reservoirs. This study took arene dolomites, stromatolite dolomites and thrombolite dolomites of the Lower Cambrian Xiaoerbulake Formation in the Tarim Basin as an example, used 0.2% acetic acid solution instead of organic acids of burial environment, carried out dissolution simulation experiments of dolomite reservoirs in the condition of high temperature and high pressure. The results showed three different samples' porosity was improved in different temperatures and pressures, but their permeability increased exponentially. The reservoir space of arene dolomites changed from pores to pores and vugs, while the reservoir space of stromatolite dolomites and thrombolite dolomites changed from pores to pores and solution fractures. It implied that organic acid had a strong solubility to dolomites, and the initial pore structure controlled the final reservoir space type. With the dissolution from homogeneous to heterogeneous, the vugs and solution fractures developed heterogeneously, and reservoir connectivity was partly improved. So, burial dissolution is of great importance in reforming the permeability of dolomite reservoirs.

Recovery method for total porosity of shale based on porosity origin: A case study of the lower part of the third member of Shahejie Formation in the Dongying Sag, Bohai Bay Basin

Wang Baohua, Lu Jianlin, Li Hao, Song Zhenxiang, Zuo Zongxin

2017, 39(5): 724-728. doi: 10.11781/sysydz201705724

Abstract(764) PDF-CN(211)

Abstract:
There are many types of pores in shale, which provide an important permeable-storage space for oil and gas enrichment. The restoration of shale pore evolution is the key to the evaluation of shale oil and gas resources and the optimization of zone, and it is also an important basis for the study of hydrocarbon expulsion process. The compaction of mud shale which reduces pore, hydrocarbon generation which forms pore, and tectonic effect which forms fracture are important mechanisms of shale pore generation. Based on these three kinds of pore forming mechanisms, a mudstone compaction model was used to calculate the porosity change of shale at different depths. The relationship between organic pore and organic carbon content during geologic evolution was modeled according to the measured data such as vitrinite reflectance, organic carbon content and physical properties of shale. After modeling the evolutionary trend of different pore types, a the multi-type shale pore recovery method based on pore formation was established based on comprehensive tectonics, facies, diagenesis and stress field characteristics. The evolution of three pore types in the lower part of the third member of Shahejie Formation in the Dongying Sag was restored by this method, and the spatial distribution of pores of different genetic types was predicted. The distribution of the total porosity of shale was determined. The forecast results are in good agreement with the real drilling data.

Zhang Zhirong

2017, 39(5): 729-729.

Abstract(324) PDF-CN(175)

Abstract:

2017 Vol. 39, No. 5

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