川中高石梯区块震旦系灯影组岩溶储层特征与储渗体分类评价

四川盆地中部地区(以下简称川中地区)震旦系灯影组四段(以下简称灯四段)气藏是以丘滩复合体沉积与表生岩溶作用为主、多因素叠加形成的大型气田,现有行业标准在表征该地区岩溶储层特征上存在着局限性。为此,借助于川中地区高石梯区块岩心观察、常规—成像测井手段,结合配套CT扫描、薄片鉴定结果,利用储渗空间搭配关系对该区内灯四段储层进行类型划分,再基于三维地震资料,以岩溶储层类型的精细刻画为约束,井震结合分析丘滩复合体展布、缝洞发育分布、优质储层分布、优质储层储量丰度,并结合实际生产资料,建立灯四段白云岩岩溶储渗体分类标准,开展储渗体划分与分类研究,明确各类储渗体动态、静态特征,优选有利开发储渗体目标。研究结果表明:①研究区灯四段岩溶储层可划分为孔隙型、孔隙—溶洞型、裂缝—孔洞型等3种类型,其中后两者具有物性好、开采动用较容易、测试效果好的优点,为灯影组优质岩溶储层类型;②建立了岩溶储渗体分类标准,将研究区储渗体细分为3类,其中一、二类储渗体投产井稳产能力较强、生产效果较好,能够实现效益开发;③该区内可划分出一类储渗体7个,二类储渗体10个,三类储渗体15个,一、二类储渗体天然气动态储量介于21.69×10~8~37.08×10~8 m~3。结论认为,该区一、二类储渗体缝洞搭配关系好、优质储层厚度大、储量丰度大、生产效果好,可以作为有利的天然气开发目标。

Characteristics and reservoir body classification & evaluation of Sinian Dengying karst reservoirs in the Gaoshiti Block of central Sichuan Basin

The gas reservoir of the 4th Member of Sinian Dengying Fm (hereinafter referred to as Deng 4 Member) in central Sichuan Basin is a large gas field formed by the superposition of multiple factors which mainly consist of mound-shoal complex sedimentation and epigenetic karstification. And the existing industrial standards are limited in characterizing the features of the karst reservoirs in this area. In this paper, the karst reservoirs of Deng 4 Member in the Gaoshiti Block of central Sichuan Basin were classified based on its core observation, conventional–image logging, combined CT scanning and thin section analysis results, as well as the matching relationship of reservoir space. Then, based on three-dimensional seismic data and with the fine characterization of karst reservoir types as a constraint，the distribution of the mound-shoal complex, the development and distribution of fractures and pores, the distribution of high-quality reservoirs and the reserve abundance of high-quality reservoirs were analyzed by means of well-seismic combination. Finally, combined with actual production results, the classification criterion for the Dengying Fm karst reservoir bodies was established, and reservoir body classification and division study was carried out so as to define the dynamic & static characteristics of all types of reservoir bodies and select the target reservoir bodies with favorable development conditions. And the following research results were obtained. First, the karst reservoirs of Deng 4 Member in the study area are divided into three types, i.e., pore type, pore–vuggy type and fracture–vuggy type, and the latter two types are high-quality reservoirs of Dengying Fm, with good physical property, exploitation effect and testing results. Second, the classification criterion of karst reservoir body is established, and according to this criterion, the karst reservoir bodies in the study area are divided into three types. Type I and II have a stable production capacity and good production effect, and can realize beneficial development. Third, there are 7 type I reservoir bodies, 10 type II reservoir bodies and 15 type III reservoir bodies. The dynamic gas reserves of type I and II reservoir bodies range from 2.169 to 3.708 billion m3. It is concluded that type I and II reservoir bodies are characterized by good fracture–vuggy matching relationship, large thickness of high-quality reservoirs, high reserve abundance and good production effect, and they can be taken as favorable development targets of natural gas.