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Wei C.,University of Wyoming | Wei C.,University of Houston | Wang H.,National Energy Shale Gas R and periment Center | Wang H.,Petrochina | And 4 more authors.
Society of Petroleum Engineers - SPE Canadian Unconventional Resources Conference 2012, CURC 2012 | Year: 2012

The shale gas development has more than 3 decades of history. In China, the development is still in the early stage due the technology limitation. The estimated technically recoverable shale gas reserve is 882 Tcf in China. The predicted shale gas production in 2020 is 3.5 Tcf which will contribute 26% of natural gas consumption in China. In order to stabilize the gas output to meet the demand of economic development, increasing recoverable shale gas reserve becomes more and more important. In this study, a Qiongzhusi reservoir was taken as an example to investigate the potential of shale gas in southern China. The methodologies involved in this investigation include experimental study on core analysis with Total Organic Content (TOC) and Vitrinite Reflectance, outcrops study, geostatistical analysis, and geo-modeling. Besides these methods, an irreplaceable step was to compare the reservoir conditions of given reservoir with successful developments in Barnett and Marcellus in the United States. By integrating all above technologies and methods, the study forecasted the sedimentary facies, estimated shale gas distribution, and evaluated the petrophysical properties of the shale play. The result indicates that most of the Qiongzhusi reservoirs have promising thickness, favorable kerogen type (type I), high TOC, and encouraging maturity. This paper also predicted favorable zones in the middle and upper Yangtze area with properties of thickness more than 60 meters, TOC not less than 2.0%, and Vitrinite Reflectance from 2.5% to 4.6%. The study would bring the reservoir engineers and geologists with detailed evidence to support the development of Qiongzhusi reservoirs, and furthermore, it offers the methodology to the research of other shale plays with similar properties. Copyright 2012, Society of Petroleum Engineers. Source

Zou C.,Petrochina | Dong D.,Petrochina | Dong D.,National Energy Shale Gas R and periment Center | Wang Y.,Petrochina | And 17 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2015

The main factors controlling the enrichment and high yield of shale gas were analyzed based on the recent research progress of depositional model and reservoir characterization of organic-rich shale in China. The study determines the space-time comparison basis of graptolite sequence in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation and proposes the important depositional pattern of marine organic-rich shale: stable ocean basin with low subsidence rate, high sea level, semi-enclosed water body, and low sedimentation rate. Deposited in the stage of Late Ordovician-Early Silurian, the superior shale with thickness of 20-80 m and total organic carbon (TOC) content of 2.0%-8.4% was developed in large deep-water shelf environment which is favorable for black shale development. Based on the comparison among the Jiaoshiba, Changning and Weiyuan shale gas fields, it is believed that reservoirs of scale are mainly controlled by shale rich in biogenic silica and calcium, moderate thermal maturity, high matrix porosity, and abundant fracture. The shales in the Wufeng and Longmaxi formations are characterized by porosity of 3.0%-8.4%, permeability of 0.0002×10-3-0.5000×10-3 μm2, stable areal distribution of matrix pore volume and their constituents, great variation in fracture and pore characteristics among different tectonic regions as well as different well fields and different intervals in the same tectonic. The Cambrian Qiongzhusi shale features poor physical properties with the porosity of 1.5%-2.9% and the permeability of 0.001×10-3-0.010×10-3 μm2, resulted from the carbonization of organic matter, high crystallinity of clay minerals and later filling in bioclastic intragranular pores. Four factors controlling the accumulation and high production of shale gas were confirmed: depositional environment, thermal evolution, pore and fracture development, and tectonic preservation condition; two special features were found: high thermal maturity (Ro of 2.0%-3.5%) and overpressure of reservoir (pressure coefficient of 1.3-2.1); and two enrichment modes were summarized: "structural sweet spots" and "continuous sweet area". © 2015, Science Press. All right reserved. Source

Liu D.,China University of Geosciences | Liu D.,Petrochina | Liu D.,National Energy Shale Gas R and periment Center | Tang S.,China University of Geosciences | And 6 more authors.
Chemical Engineering III - Proceedings of the 3rd SREE Conference on Chemical Engineering, CCE 2013 | Year: 2014

There are broad areas of shale gas exploration in China. Mainly distributed in marine basins of paleozoic and continental basins of Cenozoic and Mesozoic. Marine shale of Paleozoic in china is favored regions for shale gas accumulation, with characteristics of wide distribution, large thickness, highTOC, and suitable maturity. CNPC has conducted lots of works on field explorations, potential estimations, target screenings, delineation drillings, technology researches, pilot constructions. Most of our work is concentrated on two areas, the Sichuan Basin and Dianqianbei depression basin. According to present studies, three favorable exploration areas are screened out in lower Palaeozoic group. They are Weiyuan, Changning and Fushun-Yongchuan areas. With low exploration degree of shale gas and not in-depth of resource evaluation and investigation, seeking enrichment areas of shale gas is undoubtedly a primary task to develop commercially. And horizontal well fracturing technologies should be studied deeply. Source

Fang C.-H.,China University of Petroleum - Beijing | Fang C.-H.,National Energy Shale Gas R and periment Center | Fang C.-H.,Key Laboratory of Unconventional Oil and Gas | Huang Z.-L.,China University of Petroleum - Beijing | And 6 more authors.
Natural Gas Geoscience | Year: 2014

During the exploitation of shale gas, it is necessary to conduct reservoir reconstruction for the purpose of economic recovery. Workers in North America and China now adopt the method of combining drilling and completion of horizontal well with massive hydraulic fracturing, which needs enormous amount of water and sand. The interaction of these fluids and reservoir rocks lays the foundation for the success of reservoir reconstruction, whereas the initial water saturation of reservoirs and the understanding of causes of this state are premises of the method. With studies of the marine shale gas reservoirs in southern China, it is found that gas-enriched reservoir often has ultra-low water saturation, which is caused by hydrocarbon generation, consumption and evaporation, etc. Ultra-low water saturation improves adsorption capacity of shale, extends the movable pore throat radius, and increases the gas phase permeability. However, it also accelerates the water-base rates of adsorption and permeation, deteriorates water and hydrocarbon phase trapping problems, and brings more potential damages to aqueous phase trapping of shale gas. Under this circumstance, more attention needs to be paid to the negative effect of ultra-low water saturation and its work damage during the evaluation, reconstruction, and development of shale gas reservoirs. Source

Zhang Q.,Petrochina | Zhang Q.,National Energy Shale Gas R and periment Center | Liu R.,Petrochina | Liu R.,National Energy Shale Gas R and periment Center | And 7 more authors.
Marine and Petroleum Geology | Year: 2016

Due to the large thickness and richness of organic matter in Longmaxi shale, southeastern Chongqing is considered as the most promising area for shale gas exploration and development and was a focus of numerous research interests in China. Characterization on the pore system of organic rich shale is significant for the reserve estimation and better understanding the production mechanism of shale gas plays. Shale composition, detected by X-ray diffraction, indicates that brittle minerals, especially quartz was the most prevalent component, with average contents of 41.72 wt.%. Pore types was classified by using a combination of argon-iron milling and field emission scanning electron microscopy (FESEM), and six types of pores were observed in rock images. High pressure mercury intrusion and low pressure N2 adsorption were performed to extract the pore size distribution of Longmaxi shale. The results show that the nanopore was the major pore type in shale samples, which accounts for 95.6% of the pore volume. In the nanopore system, pore with diameters between 2 nm and 10 nm is the major component that contributes 76% of the total pore volume and 78% of the whole inner surface area. Furthermore, the dominant pore shape was interpreted from the adsorption-desorption hysteresis loop shape, and the typical slit-shaped pores were identified in the examined shale samples. Based on single factor analysis method, organic matter richness is the main controlling factor for the volume of nanopore and the specific surface area. No direct correlation between brittle minerals and nanopores, but high quartz and calcite content makes it much easier for the formation to generate natural fractures and to be hydraulically fractured. The study can inspire and guide shale gas exploration and exploitation southeastern Chongqing to some extent. © 2015 Elsevier Ltd. Source

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