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Shale Gas Accumulation Conditions and Gas‐bearing Properties of the Lower Cambrian Shuijingtuo Formation in Well Chengtan 1, Dabashan Complex Tectonic Belt
Author(s) -
LIU Bin,
CHENG Jing,
YE Jun,
WANG Sheng
Publication year - 2015
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12303_5
Subject(s) - shale gas , geology , tectonics , geochemistry , bearing (navigation) , oil shale , paleontology , earth science , petroleum engineering , petrology , geography , cartography
junction of the Yangtze plate and North China plate, which is the composite products of the Indo-Chinese epoch, Yanshan epoch, Himalayan epoch thrust nappe. Experiencing multiphase complex structural movement, the tectonic belt has been regarded as a forbidden zone in the oil and gas exploration. And it is also a blank area of oil and gas exploration. It has been confirmed by the rock samples of outcrop and the downhole core samples of the geological survey well that the geochemical characteristics of the shale of the Lower Cambrian Shuijingtuo Formation in the Dabashan complex tectonic belt of the northeast of Chongqing, and the shale in the middle-shallow layer has showed good hydrocarbon content. This study evaluates shale gas accumulation conditions and gas bearing properties of the Lower Cambrian Shuijingtuo Formation of the mid-deep layer in this tectonic belt. An optimal parameter well of shale gas in the Shuijingtuo Formation, Chengtan 1, was selected and drilled for the first time in the Dabashan area of the northeast of Chongqing. This well finished at the depth of 2727 meters, beginning in the the Lower Cambrian Shuijingtuo Formation, ending in the top of Dengying Formation. Collectively, it revealed the presence of dark shale series in the Shuijingtuo Formation up to 1234 meters (apparent thickness), i.e., the thickest black shale series encountered during single vertical well drilling in the Yangtze platform.In addition to, it revealed the shale gas of 416 meters, for vertical well drilling at present in China meet shale gas thickness. Based on laboratory analysis data, and combined with logging, well logging and seismic data, it is verified that the dark shale of Shuijingtuo Formation in Well Chengtan1 is gifted with high organic carbon content (1-38%, an average of 6.5%), moderate organic maturity (1.8-2.4%), high brittle mineral content (74%), various types of reservoir rock and pore (The main reservoir rock types include black shale, siliceous mudstone, carbonaceous mudstone and silty mudstone, silicalite, and carbon breccia. The main pore types have organic pore, intercrystalline pore, intragranular pore, and mylonitization hole), and well developed meso/ micropores and faults. Because of several strong nappe extrusion effect, a special tectonic geology model is formed in this area that it features the target stratum of Shuijingtuo Formation exposing to the surface, high formation clination (60-90°), complicated fault system (200 fault/km), and repeatedly superposition of the target stratum of Shuijingtuo Formation. On account of the good reservoir and geochemical characteristics, and the special tectonic geology model, the unique shale gas accumulation condition is formed in this area. The black shale in the LIU Bin, CHENG Jing, YE Jun and WANG Sheng, 2015. Shale Gas Accumulation cConditions and Gas-bearing Properties of the Lower Cambrian Shuijingtuo Formation in Well Chengtan 1, Dabashan Complex Tectonic Belt. Acta Geologica Sinica (English Edition), 89 (supp.): 162-163.