川西马井气田蓬莱镇组致密砂岩储层可动水饱和度计算方法

摘要

马井气田主力产气层段为侏罗系蓬莱镇组地层,该地层主要是具有复杂岩性、复杂孔隙结构、低孔隙度低渗透率等特点的致密砂岩储层,储层岩电参数之间表现出明显的非阿尔奇现象,使得常规阿尔奇模型难以准确计算储层含水饱和度;现有的建立在常规砂岩储层中的束缚水饱和度模型在复杂孔隙结构致密砂岩储层中应用效果较差,利用阿尔奇含水饱和度与常规束缚水饱和度的差值难以准确确定储层可动水饱和度.在储层基本特征分析的基础上,结合岩电实验数据研究认为双孔隙导电体积模型能较好表征储层的导电规律;在双孔隙导电体积模型的基础上,推导建立了可动水饱和度计算模型.基于岩电实验、核磁共振束缚水饱和度测试结果以及常规测井数据,分析了模型中的各个参数,提出确定束缚水饱和度的新方法,进而确定了模型中微孔孔隙度这一关键参数.现场实例应用表明,可动水饱和度计算结果与储层产水特征相符,利用计算的可动水饱和度判别储层中流体的可动性运用效果较好.%The gas field in Majing is located in the depression of the western Sichuan basin,its main production formation is Penglaizhen formation in Jurassic.The formation is mainly tight sandstone reservoirs which are of the characteristics such as complex lithology,complicated pore structure,low porosity and permeability.The parameters of rock electrical property experiment from the reservoirs show an obvious non-Archie phenomenon on account of their characteristics,so conventional Archie model can't calculate water saturation accurately.Meanwhile,the irreducible water saturations which are constructed in conventional sandstone reservoirs are less effective for the tight sandstone reservoirs with complicated pore structure.The result from the water saturation calculated by Archie model subtracting irreducible water saturations calculated by conventional irreducible water saturations model can't represent the mobile water saturation precisely.In this paper,combining rock electrical property experiments data on the basis of the analysis of the basic characteristics of the reservoirs,it's clear that the dual-porosity conducting volume model constructed on the complicated pore structure can better present the conducting law,and deduce the calculation model of mobile water saturation on the basis of the dual-porosity conducting volume model.We analyze all parameters of the model on the basis of rock electrical property experiments,irreducible water saturation of the NMR test and conventional logging data,and proposed a new method to calculate the irreducible water saturation which can convert to determine the micro-porosity.Practical examples show that the result of mobile water saturation calculation is consistent with water production characteristics of reservoirs,simultaneously it is a good result when the calculated mobile water saturations are used to distinguish the fluid mobility.