Method for Calculating Single-Well Producing Geological Reserves and Single-Well Technically Recoverable Reserves in Tight Sandstone Gas Reservoirs: A Case of Carboniferous-Permian Gas Reservoirs in Yanchang Gas Field, Ordos Basin

doi:10.7657/XJPG20220315

Abstract

Abstract:

The Carboniferous-Permian sandstone gas reservoirs in the Ordos basin are tight, with obvious different gas saturations from part to part of the reservoir unit, complex gas-bearing pattern, non-uniform reservoir pressure systems, and highly heterogeneous distribution of reserves as a whole. This paper compared the geological and development characteristics between Carboniferous-Permian tight sandstone gas reservoirs and the conventional sandstone gas reservoirs in Yanchang gas field in Ordos basin. It is found that there is a threshold pressure gradient during the development of the Carboniferous-Permian tight sandstone gas reservoirs, and the single-well produced geological reserves and the single-well reserves producing radius increase with the decrease of the bottom hole pressure. When the abandonment pressure is reached, the single-well produced geological reserves and the single-well reserves producing radius reach the maximum values. Accordingly, by analyzing the distribution of reserves during the development of tight sandstone gas reservoirs, the material balance equation under the condition of threshold pressure gradient was established, and the relationship between cumulative production and bottom hole pressure was obtained. Furthermore, two methods for calculating the threshold pressure gradient were analyzed. On this basis, the method for calculating the single-well producing geological reserves and the single-well technically recoverable reserves in tight sandstone gas reservoirs was proposed, which provides a theoretical basis for the optimization of well pattern to develop tight sandstone gas reservoirs. The theoretical calculation method has been improved to form a simplified method for calculating single-well producing geological reserves, which is referential for well pattern deployment in undeveloped blocks.

Key words: Ordos basin, Yanchang gas field, Carboniferous, Permian, tight sandstone gas reservoir, threshold pressure gradient, recoverable reserves, producing reserves

CLC Number:

TE313.8

CHEN Zhanjun, REN Zhanli. Method for Calculating Single-Well Producing Geological Reserves and Single-Well Technically Recoverable Reserves in Tight Sandstone Gas Reservoirs: A Case of Carboniferous-Permian Gas Reservoirs in Yanchang Gas Field, Ordos Basin[J]. Xinjiang Petroleum Geology, 2022, 43(3): 360-367.

Figures/Tables 7

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Table 1.

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Table 2.

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特征		常规砂岩气藏	鄂尔多斯盆地延长气田石炭系—二叠系致密砂岩气藏
地质特征	储集层物性	中—特高孔、中—特高渗	低—特低孔、低—特低渗
	气藏分布	有正常的气水分界面	气水主要为混合相态
	含气饱和度	气藏单元内含气饱和度相对均一或规律	含气规律复杂
	气藏压力	统一压力系统	压力系统不统一
开发特征	单井产能	单井产量高	主要为中—低产井
	生产见水	初期不见水,后期快速见水,定容气藏基本不见水	大部分井不易见水,部分井少量见水
	储量动用	理想状态下,最大单井动用地质储量即气藏地质储量	单井动用地质储量随井底压力降低而增加,最大单井动用地质储量受废弃压力、启动压力梯度控制,与总地质储量无明显关系
	技术可采储量	大于70%	30%~40%
	生产压力分布	气藏各部位压力统一下降,井底压力可恢复至气藏平均压力	在气藏中形成压降漏斗,最多可恢复成斜率等于启动压力梯度的压降锥
	剩余储量分布	相对均匀	距井点越近,剩余储量越少

地层	井名	气藏拟临界压力/MPa	气藏拟临界温度/K	原始气藏压力/MPa	气藏温度/ K	气藏拟对比压力	气藏拟对比温度	原始气藏偏差系数
盒8段	Y102井	4.598	194.02	25.903	367.53	5.63	1.89	0.951
	Y153井	4.598	194.02	23.737	367.81	5.16	1.90	0.947
	Y103井	4.598	194.02	21.808	365.82	4.74	1.89	0.926
山1段	Y399井	4.608	190.90	19.611	373.10	4.26	1.95	0.927
	Y539井	4.608	190.90	18.851	376.88	4.09	1.97	0.932
	Y114井	4.608	190.90	20.525	382.36	4.45	2.00	0.943
	Y536井	4.608	190.90	20.702	373.60	4.49	1.96	0.945
山2段	Y249井	4.697	194.68	21.625	385.89	4.60	1.98	0.946
	Y131井	4.697	194.68	21.625	385.89	4.60	1.98	0.946
	Y450井	4.697	194.68	23.381	377.13	4.98	1.94	0.943
	Y369井	4.697	194.68	22.168	380.03	4.72	1.95	0.925
	Y454井	4.697	194.68	21.501	372.31	4.58	1.91	0.924
	Y532井	4.697	194.68	24.100	370.56	5.13	1.90	0.947
本溪组	Y393井	4.694	194.75	27.976	384.38	5.96	1.97	0.972
	Y504井	4.694	194.75	27.044	387.45	5.76	1.99	0.970
	Y448井	4.694	194.75	24.918	383.67	5.31	1.97	0.955
	Y151井	4.694	194.75	30.775	388.30	6.56	1.99	0.983
	Y367井	4.694	194.75	27.217	394.71	5.80	2.03	0.973
	Y364井	4.694	194.75	29.930	379.09	6.38	1.95	0.981
	Y370井	4.694	194.75	29.681	381.45	6.32	1.96	0.979