Mechanism of hydrocarbon accumulation and enrichment of tuffaceous tight oil with separate reservoir and source rock: A case study of tuff reservoir from the Permian Tiaohu Formation in the Santanghu Basin, northwest China

AAPG Bulletin ◽  
2019 ◽  
Vol 103 (2) ◽  
pp. 345-367 ◽  
Author(s):  
Jian Ma ◽  
Zhilong Huang ◽  
Tianjun Li
Keyword(s):  
Source Rock ◽  
Northwest China ◽  
Tight Oil ◽  
Hydrocarbon Accumulation ◽  
Accumulation And Enrichment

Oil–source rock correlation for tight oil in tuffaceous reservoirs in the Permian Tiaohu Formation, Santanghu Basin, northwest China

2015 ◽  
Vol 52 (11) ◽  
pp. 1014-1026 ◽  
Author(s):  
Jian Ma ◽  
Zhilong Huang ◽  
Xiaoyu Gao ◽  
Changchao Chen
Keyword(s):  
Organic Matter ◽  
Crude Oil ◽  
Source Rock ◽  
Stable Carbon Isotope ◽  
Northwest China ◽  
Source Rocks ◽  
Tight Oil ◽  
Stable Carbon ◽  
Lucaogou Formation ◽  
Oil Source

Tight oil in the Permian Tiaohu Formation in the Santanghu Basin, northwest China, has a peculiar property such that the reservoir is sedimentary organic matter-bearing tuff characterized by high porosity (10%–25%) and very low permeability, mainly in the range of 0.01–0.50 mD. Biomarker and stable carbon isotope compositions of selected crude oils and source-rock extracts were analyzed to determine the source rock of the tight oil. Source rocks in the Lucaogou Formation consist of various rock types dominated by mudstones containing organic matter with intense yellow–green fluorescence. Mudstones in the Lucaogou Formation have total organic carbon (TOC) values mainly in the range of 1.0–8.0 wt%, hydrocarbon generation potential (S1 + S2) mostly >6 mg/g, and chloroform extractable bitumen “A” generally >0.1%. The maceral composition is predominantly fluorescing amorphinite. The hydrogen index (HI) varies from 300 to 900 mg HC/g TOC, indicating dominant Type I and Type II kerogen. Compared with the mudstones and tuffs in the Tiaohu Formation, the mudstones in the Lucaogou Formation are the best source rocks. The biomarker characteristics of mudstone extracts in the Lucaogou Formation differ from those in the Tiaohu Formation, based on the gammacerane index, β-carotane content, and the relative contents of C27, C28, and C29 regular steranes. Crude oil samples in the tuff show low pristane/phytane (Pr/Ph) ratios, high gammacerane indices, high β-carotane, and a dominance of the C29 regular sterane followed by C28 and C27 steranes, as well as depleted stable carbon isotope compositions. Oil–source correlation with biomarkers and δ13C values shows that the crude oil in the tuffs mainly originates from underlying source rocks in the Lucaogou Formation. The sedimentary organic matter in the tuffs also makes a small contribution to the tuffaceous reservoir. Therefore, the tuffaceous tight reservoir in the Tiaohu Formation is unusual in that the oil is not indigenous; rather, it migrates a long distance to accumulate in the upper reservoir.

scholarly journals Characteristics and formation mechanisms of tight oil: A case study of the Huahai Depression, Jiuquan Basin, Northwest China

2018 ◽  
Vol 37 (1) ◽  
pp. 296-314
Author(s):  
Chunyan Fan ◽  
Xianglu Tang ◽  
Yuanyin Zhang ◽  
Yan Song ◽  
Zhenxue Jiang ◽  
...  
Keyword(s):  
Northwest China ◽  
Gas Chromatography Mass Spectrometry ◽  
Formation Mechanisms ◽  
Tight Oil ◽  
Oil Accumulation ◽  
Tight Reservoir ◽  
Formation Pattern ◽  
Porosity And Permeability ◽  
Carbonate Cementation

The exploration of tight oil reservoirs has achieved a big success, especially in the Huahai Depression, Jiuquan Basin, China, but the characteristics and formation mechanisms of the tight oil reservoir are unclear. In this paper, a series of analyses including thin section, scanning electron microscope, gas chromatography–mass spectrometry, isotope, and fluid inclusions were taken to study the tight reservoirs of the Xiagou Formation (K1g) and Zhonggou Formation (K1z) in the Huahai Depression. The results show that the main factors influencing the porosity and permeability of the tight reservoir are the compaction and two periods of carbonate cementation. The second type of carbonate cementation was related to the decarboxylation of organic acids in parts of the study area. The tight oil accumulation periods for different formations are confirmed, during 115–102 Ma in K1g1, 114–97 Ma in K1g2, and 103–85 Ma in K1z1, respectively. The tight oil migrations are executed for only several meters vertically but hundreds of meters even kilometers laterally. Two kinds of formation mechanisms exist in the study area. The main formation pattern is the “hydrocarbon accumulated after reservoir had tightened,” which has occurred in most of the study area. The other pattern, the “hydrocarbon accumulated during reservoir was tightening,” is found in several places of the study area.

Hydraulic Fracturing of Ultrahigh Stress Tight Oil Reservoir - A Case Study of Yumen Oilfield in China

2016 ◽  
Author(s):  
Peng Yi ◽  
Weng Dingwei ◽  
Xu Yun ◽  
Wang Liwei ◽  
Lu Yongjun ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Tight Oil ◽  
Oil Reservoir ◽  
Tight Oil Reservoir
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