大型致密砂岩气田气水分布规律及控制因素——以鄂尔多斯盆地苏里格气田西区为例

Water and gas distribution and its controlling factors of large scale tight sand gas:A case study of western Sulige gas field,Ordos Basin,NW China

以储集层地质特征为基础,分析苏里格气田西区地层水的化学特征和赋存状态,明确研究区气水分布规律及控制因素。苏里格气田西区含水层大面积广泛分布,气层发育差且分布局限,纵向上气、水层呈孤立状交叉分布,储集单元内部气水分异不明显,没有统一的气水界面,总体下石盒子组盒8下段和山西组山1段好于盒8上段。气水分布主要受生烃强度、储集层距烃源岩的距离、砂泥岩的配置关系及复合砂体内部物性差异等因素的控制,其中生烃强度控制了气水分布的宏观格局,随着生烃强度由高到低,由良好的天然气聚集逐渐向气水伴生气藏变化;储集层距烃源岩越近,气层相对越发育,反之则气水同层和含气水层越发育;砂泥岩的配置关系和复合砂体内部物性差异主要控制天然气的局部充注、聚集成藏,由此归纳出5种气水分布模式:纯气型、巨厚储集层气水混存型、上水下气型、上气下水型和上下水夹气型。

The chemical characteristics and occurrence state of formation water in western Sulige gas field were analyzed based on geological features of reservoirs, the gas and water distribution regularity and the main controlling factors were determined. Aquifer zones are widely distributed in the whole Western Sulige gas field, gas zones developed poorly and distributed limitedly. Vertically, gas and water zones are of poor continuity and distributed in an isolated and staggered pattern. Inside the gas reservoir, there is not a uniform gas and water interface because of the hard differentiation between gas and water. On the whole, the lower segment of H8 Member in Shihezi Formation and S 1 Member in Shanxi Formation are both better than the upper segment of H8 Member. Gas and water distribution of Western Sulige gas field is mainly controlled by gas-generating intensity, the distances between reservoirs and hydrocarbon source rocks, configuration relationship of sand shale and physical property differences inside sand body complex. Among them, gas-generating intensity mainly controls the macro pattern of gas and water distribution, with the decrease of gas-generating intensity, good gas accumulation gradually changes to be water associated gas reservoir. The closer the distance between reservoirs and hydrocarbon source rocks, the more developed the gas zones, on the contrary, the gas-bearing water zone and coexisting gas and water zone are more developed. Sand shale configuration relationship and physical property differences inside sand body complex mainly control the local gas filling and accumulation. Five types of gas and water distribution patterns are summarized： pure gas, thick reservoir with mixed gas and water, water above the gas, gas above the water, and gas sandwiched between water.