Characteristics of Shale Reservoir and Sweet Spot Identification of the Lower Cambrian Niutitang Formation
in Northwestern Hunan Province, China |
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作者姓名: | QIN Mingyang CAO Zheng GUO Jianhu HUANG Yanran SUN Lianpu DONG Li |
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作者单位: | 1 Central South University Press, Changsha 410083, China
2 School of Geosciences and Info-Physics Engineering, Central South University, Changsha 410083, China
3 The Survey Academy of Coal Geology in Hunan, Changsha 410014, China,4 School of Geosciences, China University of Petroleum, Qingdao 266580, China
5 School of Petroleum Engineering, Chongqing University of Science and Technology, Chongqing 401331, China,2 School of Geosciences and Info-Physics Engineering, Central South University, Changsha 410083, China,2 School of Geosciences and Info-Physics Engineering, Central South University, Changsha 410083, China;6 Hunan Provincial Key Laboratory of Shale Gas Resource Utilization, Hunan University of Science and Technology, Xiangtan, 411201, China,7 Sino Geotech (Beijing) Science & Technology Co., Ltd. Beijing 100020, China and 8 Exploration & Production Research Institute SINOPEC, Beijing 100083, China
9 Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral; Shandong University of Science and Technology, Qingdao 266590, China |
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基金项目: | This work is granted by the National Natural Science Foundation of China;the Natural Science Foundation of Hunan Province |
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摘 要: | The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs;study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niutitang Formation(Fm),Southern China.In this study,core observation and lithology study were conducted along with X-ray diffraction(XRD)and electronic scanning microscopy(SEM)examinations and liquid nitrogen(N_2)adsorption/desorption and CH_4 isothermal adsorption experiments for several exploration wells in northwestern Hunan Province,China.The results show that one or two intervals with high-quality source rocks(TOC2 wt%)were deposited in the deep-shelf facies.The source rocks,which were mainly composed of carbonaceous shales and siliceous shales,had high quartz contents(40 wt%)and low clay mineral(30 wt%,mainly illites)and carbonate mineral(20 wt%)contents.The SEM observations and liquid nitrogen(N_2)adsorption/desorption experiments showed that the shale is tight,and nanoscale pores and microscale fractures are well developed.BJH volume(V_(BJH))of shale ranged from 2.144×10~(-3) to 20.07×10~(-3) cm~3/g,with an average of11.752×10~(-3) cm~3/g.Pores mainly consisted of opened and interconnected mesopores(2–50 nm in diameter)or macropores(50 nm in diameter).The shale reservoir has strong adsorption capacity for CH_4.The Langmuir volume(V_L)varied from1.63 to 7.39 cm~3/g,with an average of 3.95 cm~3/g.The characteristics of shale reservoir are controlled by several factors:(1)A deep muddy continental shelf is the most favorable environment for the development of shale reservoirs,which is controlled by the development of basic materials.(2)The storage capacity of the shale reservoir is positively related to the TOC contents and plastic minerals and negatively related to cement minerals.(3)High maturity or overmaturity leads to the growth of organic pores and microfractures,thereby improving the reservoir storage capacity.It can be deduced that the high percentage of residual gas in Niutitang Fm results from the strong reservoir storage capacity of adsorbed gas.Two layers of sweet spots with strong storage capacity of free gas,and they are characterized by the relatively high TOCcontents ranging from 4 wt%to 8 wt%.
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修稿时间: | 2018/12/20 0:00:00 |
Characteristics of Shale Reservoir and Sweet Spot Identification of the Lower Cambrian Niutitang Formation in Northwestern Hunan Province,China |
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Authors: | QIN Mingyang CAO Zheng GUO Jianhu HUANG Yanran SUN Lianpu and DONG Li |
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Abstract: | The accumulation and productivity of shale gas are mainly controlled by the characteristics of shale reservoirs; study of these characteristics forms the basis for the shale gas exploitation of the Lower Cambrian Niutitang Formation (Fm), Southern China. In this study, core observation and lithology study were conducted along with X‐ray diffraction (XRD) and electronic scanning microscopy (SEM) examinations and liquid nitrogen (N2) adsorption/desorption and CH4 isothermal adsorption experiments for several exploration wells in northwestern Hunan Province, China. The results show that one or two intervals with high‐quality source rocks (TOC>2 wt%) were deposited in the deep‐shelf facies. The source rocks, which were mainly composed of carbonaceous shales and siliceous shales, had high quartz contents (>40 wt%) and low clay mineral (<30 wt%, mainly illites) and carbonate mineral (<20 wt%) contents. The SEM observations and liquid nitrogen (N2) adsorption/desorption experiments showed that the shale is tight, and nanoscale pores and microscale fractures are well developed. BJH volume (VBJH) of shale ranged from 2.144×10–3 to 20.07×10–3 cm3/g, with an average of 11.752×10–3 cm3/g. Pores mainly consisted of opened and interconnected mesopores (2–50 nm in diameter) or macropores (>50 nm in diameter). The shale reservoir has strong adsorption capacity for CH4. The Langmuir volume (VL) varied from 1.63 to 7.39 cm3/g, with an average of 3.95 cm3/g. The characteristics of shale reservoir are controlled by several factors: (1) A deep muddy continental shelf is the most favorable environment for the development of shale reservoirs, which is controlled by the development of basic materials. (2) The storage capacity of the shale reservoir is positively related to the TOC contents and plastic minerals and negatively related to cement minerals. (3) High maturity or overmaturity leads to the growth of organic pores and microfractures, thereby improving the reservoir storage capacity. It can be deduced that the high percentage of residual gas in Niutitang Fm results from the strong reservoir storage capacity of adsorbed gas. Two layers of sweet spots with strong storage capacity of free gas, and they are characterized by the relatively high TOC contents ranging from 4 wt% to 8 wt%. |
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Keywords: | Northwestern Hunan Province Niutitang Formation reservoir characteristics control factors sweet spots identification |
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