Source and reservoir characteristics of Upper Triassic lacustrine Chang 6 tight oil play in Zhangjiagou area, Ordos Basin, China

2021 ◽  
pp. 1-27
Author(s):  
Yan Cao ◽  
Hui Han ◽  
Shijia Chen ◽  
Rui Liu ◽  
Jingyue Zhang ◽  
...  
Keyword(s):  
Upper Cretaceous ◽  
Ordos Basin ◽  
Micropore Volume ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Major Type ◽  
Tight Oil ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
Reservoir Characteristics

To explore the source and reservoir characteristics of Chang 6 tight oil in the Zhangjiagou area, we have extracted a suite of Chang 6 tight sandstones and the source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation in the Ordos Basin, China, respectively, using chloroform. We examined group components by fractionations of extracted organic matter. Using low-pressure gas adsorptions and gas chromatography-mass spectrometry, respectively, we analyzed the pore structure of the studied samples before and after extraction and the oil source of the separate saturated hydrocarbon components. The results indicate that the porosity of the Chang 6 tight sandstone is mainly distributed in the 8%–14% range, averaging 10.5%, the permeability of the studied reservoir is only approximately 0.16 × 10−3 μm2, and the pore-throat radius is mainly less than 2 μm. The major type of pores of the reservoir includes the residual intergranular pore, secondary intergranular dissolved pore, and intragranular dissolved pore. The micropore volume of the Chang 6 tight sandstone is in the range of 0.0071–0.0092 cm3/g, and the mesopore volume of the Chang 6 tight sandstone is in the range of 0.0237–0.0343 cm3/g. The micropore volume and micropore surface area significantly increased after chloroform extractions, and soluble hydrocarbons could be stored in micropores of the Chang 6 tight sandstone. The three sets of source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation are high quality by the evaluation of source rocks, and the Chang 7 has the highest value of source rocks, followed by Chang 9 and Chang 8. The pentacyclic triterpene characteristics (Ts-C30H-C30*) of Chang 6 crude oil are similar to those of Chang 7 source rock, and the tight oil of the Chang 6 member in the Zhangjiagou area originated from Chang 7 source rocks.

scholarly journals Analysis of the charging process of the lacustrine tight oil reservoir in the Triassic Chang 6 Member in the southwest Ordos Basin, China

2017 ◽  
Vol 54 (12) ◽  
pp. 1228-1247
Author(s):  
Zhengjian Xu ◽  
Luofu Liu ◽  
Tieguan Wang ◽  
Kangjun Wu ◽  
Wenchao Dou ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Source Rocks ◽  
Driving Mechanism ◽  
Tight Oil ◽  
Geological Time ◽  
Tight Sandstone ◽  
Main Production ◽  
The Ordos Basin ◽  
Homogenization Temperatures ◽  
Quartz Grains

With the success of Bakken tight oil (tight sandstone oil and shale oil) and Eagle Ford tight oil in North America, tight oil has become a research focus in petroleum geology. In China, tight oil reservoirs are predominantly distributed in lacustrine basins. The Triassic Chang 6 Member is the main production layer of tight oil in the Ordos Basin, in which the episodes, timing, and drive of tight oil charging have been analyzed through the petrography, fluorescence microspectrometry, microthermometry, and trapping pressure simulations of fluid inclusions in the reservoir beds. Several conclusions have been reached in this paper. First, aqueous inclusions with five peaks of homogenization temperatures and oil inclusions with three peaks of homogenization temperatures occurred in the Chang 6 reservoir beds. The oil inclusions are mostly distributed in fractures that cut across and occur within the quartz grains, in the quartz overgrowth and calcite cements, and the fractures that occur within the feldspar grains, with blue–green, green, and yellow–green fluorescence colours. Second, the peak wavelength, Q650/500, and QF535 of the fluorescence microspectrometry indicate three charging episodes of tight oil with different oil maturities. The charging timings (141–136, 126–118, and 112–103 Ma) have been ascertained by projecting the homogenization temperatures of aqueous inclusions onto the geological time axis. Third, excess-pressure differences up to 10 MPa between the Chang 7 source rocks and the Chang 6 reservoir beds were the main driving mechanism supporting the process of nonbuoyancy migration.

scholarly journals Diagenesis and its influence on reservoir quality and oil-water relative permeability: A case study in the Yanchang Formation Chang 8 tight sandstone oil reservoir, Ordos Basin, China

2019 ◽  
Vol 11 (1) ◽  
pp. 37-47 ◽  
Author(s):  
Meng Wang ◽  
Zhaomeng Yang ◽  
Changjun Shui ◽  
Zhong Yu ◽  
Zhufeng Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Relative Permeability ◽  
Oil Recovery ◽  
Ordos Basin ◽  
Reservoir Quality ◽  
Tight Oil ◽  
Property A ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
Small Pore

Abstract Different from conventional reservoirs, unconventional tight sand oil reservoirs are characterized by low or ultra-low porosity and permeability, small pore-throat size, complex pore structure and strong heterogeneity. For the continuous exploration and enhancement of oil recovery from tight oil, further analysis of the origins of the different reservoir qualities is required. The Upper Triassic Chang 8 sandstone of the Yanchang Formation from the Maling Oilfield is one of the major tight oil bearing reservoirs in the Ordos Basin. Practical exploration demonstrates that this formation is a typical tight sandstone reservoir. Samples taken from the oil layer were divided into 6 diagenetic facies based on porosity, permeability and the diagenesis characteristics identified through thin section and scanning electron microscopy. To compare pore structure and their seepage property, a high pressure mercury intrusion experiments (HPMI), nuclear magnetic resonance (NMR), andwater-oil relative permeability test were performed on the three main facies developed in reservoir. The reservoir quality and seepage property are largely controlled by diagenesis. Intense compaction leads to a dominant loss of porosity in all sandstones, while different degrees of intensity of carbonate cementation and dissolution promote the differentiation of reservoir quality. The complex pore structure formed after diagenesis determines the seepage characteristics, while cementation of chlorite and illite reduce the effective pore radius, limit fluid mobility, and lead to a serious reduction of reservoir permeability.

scholarly journals Geochemical Characteristics and Origins of the Crude Oil of Triassic Yanchang Formation in Southwestern Yishan Slope, Ordos Basin

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaoli Zhang ◽  
Jinxian He ◽  
Yande Zhao ◽  
Hongchen Wu ◽  
Zeqiang Ren
Keyword(s):  
Crude Oil ◽  
Oil And Gas ◽  
Saturated Hydrocarbon ◽  
Ordos Basin ◽  
Water Environment ◽  
Geochemical Characteristics ◽  
Source Rocks ◽  
Gas Chromatography Mass Spectrometry ◽  
Yanchang Formation ◽  
Parent Materials

Biomarker compounds that derived from early living organisms play an important role in oil and gas geochemistry and exploration since they can record the diagenetic evolution of the parent materials of crude oil and reflect the organic geochemical characteristics of crude oil and source rocks. To offer scientific basis for oil exploration and exploitation for study area, gas chromatography-mass spectrometry method is applied to study the biomarker compounds of crude oil in Southwestern Yishan Slope of Ordos Basin, through qualitatively and quantitatively analyzing separated materials. The crude oil of Yanchang Formation and the source rocks of Yan’an and Yanchang Formation were collected in order to systematically analyze the characteristics of the biomarker compounds in saturated hydrocarbon fractions and clarify the organic geochemical characteristics of crude oil. The distribution and composition of various types of hydrocarbon biomarker compounds in crude oil suggest that the parent materials of crude oil are composed of hydrobiont and terrigenous plants, and the crude oil is mature oil which is formed in the weak reducing fresh water environment. Oil source correlation results show that the crude oil of Yanchang Formation in Yishan Slope is sourced from the source rocks of Chang 7 subformation.

scholarly journals Staged Fracturing of Horizontal Wells in Continental Tight Sandstone Oil Reservoirs: A Case Study of Yanchang Formation in Western Ordos Basin, China

2021 ◽  
Vol 9 ◽  
Author(s):  
Dingxue Zhang ◽  
Yunfei Liu ◽  
Hui Luo ◽  
Shixue Cao ◽  
Jingxin Cao ◽  
...  
Keyword(s):  
Horizontal Well ◽  
Ordos Basin ◽  
Production Capacity ◽  
Oil Production ◽  
Horizontal Wells ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Tight Sandstone ◽  
Yanchang Formation ◽  
Well Pattern

Continental tight sandstone oil reservoirs have strong heterogeneity, and staged fracturing technology of horizontal well is a crucial measure for successful development of oil and gas. In this study, the fracturing effect of horizontal wells in tight oil reservoirs of Yanchang Formation in the western Ordos Basin was systematically studied using the rock mechanics, array acoustic and microseismic testing data and the staged fracturing technology. The hydraulic fracturing method was used to calculate the horizontal principal stress difference (σH-σh). It showed that as the buried depth increases, σH-σh tends to decrease first and then increase. Small-scale fracturing should be used for areas with smaller σH-σh values. Fracturing construction parameters have an impact on oil production capacity, which is mainly manifested in that the usage of prepad fluid, sand-carrying fluid and proppant is proportional to productivity. Excessive displacement and construction scale should not be used in the fracturing process, and the fracture height of the target layer should be strictly controlled within the range of 26 m. The analysis of the “rupture points” in the fracturing curves shows that wells with relatively obvious rupture points usually have a higher oil production capacity. These wells have a good fracturing effect and an effective fracture network was formed in the tight oil reservoir. The optimization simulation results of the horizontal well pattern form show that the seven-point combined well pattern is the best well pattern, which is suitable for the development of tight oil sandstone in the Yanchang Formation.

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