Discussion on characteristics and reservoiring mechanism of deep basin gas in Upper Paleozoic in Ordos basin

Ma Xinhua

doi:10.11743/ogg20050216

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Discussion on characteristics and reservoiring mechanism of deep basin gas in Upper Paleozoic in Ordos basin
Vol. 26, Issue 2, Pages: 230-236(2005)
Online First：25 April 2005，

Published：2005
DOI： 10.11743/ogg20050216
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DOI：

Ma Xinhua. Discussion on characteristics and reservoiring mechanism of deep basin gas in Upper Paleozoic in Ordos basin[J]. 2005, 26(2): 230-236. DOI： 10.11743/ogg20050216.

摘要

研究区盒8、山2两大成藏组合具备深盆气的形成条件及特征

其储层具有致密化程度高、含气范围内零星产水、气藏压力分割性强等特点

主要归因于陆相沉积层序和气藏的后期改造。地质分析和物理模拟实验表明

砂岩体走向上区域连通

在成藏环境下可以发生气驱水的运聚过程。以早白垩世末为界可划分出形成发育期和深盆气改造期两个阶段。在成藏过程中气藏压力经历了由超压到负压的演变过程。引起不同地区压力降低的主控因素是不同的:苏里格庙地区主要由储层溶孔体积增大引起

温度降低也有一定影响;而东部榆林、神木-米脂地区

主要由后期抬升温度降低引起。在综合分析成藏特征和过程的基础上

提出了"广覆叠置式源顶改造型深盆气"成藏模式。

Abstract

He 8 and Shan 2 plays in the study area have the characteristics of and conditions for accumulation of deep basin gas. The reservoirs are characterized by high compactibility

sporadic water production in gas-bearing area and strong compartmentalization of gas reservoir pressure

mainly due to continental sedimentary sequence and later reconstruction of gas reservoirs. Geologic analysis and physical modelling show that sandbodies have regional connectivity (along) strike

thus migration and accumulation processes of gas displacing water might occur in reservoiring conditions. A development stage and a reconstruction stage of deep basin gas can be divided at the end of Early Cretaceous. Reservoir pressure evolved from overpressure to underpressure in the reservoiring process. The main factors that caused the pressure drops in different areas are not the same. In Suligemiao area

it is mainly caused by the enlargement of dissolution pores in reservoirs

and temperature drop also has certain influences. While in Yulin and Shenmu-Mizhi areas in eastern Ordos Basin

it is mainly caused by the uplifting and temperature drop.A specific reservoiring pattern is presented based on comprehensive analysis of reservoiring features and process.