琼东南盆地宝岛区陵水组储层特征与有利储层分布

Reservoir characteristics and favorable distribution of Lingshui Formation,Baodao area, Qiongdongnan Basin

为了明确储层物性特征、低渗透储层成因及有利储层分布,为后期成藏综合评价和油气勘探开发潜力目标优选提供地质依据,以琼东南盆地宝岛区古近系陵水组测井、铸体薄片、扫描电镜观察数据、黏土X射线衍射等资料为研究对象,系统分析了该区储层岩石学、物性与储集空间特征以及储层物性的主控因素,明确了其有利储层的发育区。研究结果表明:①该区陵水组主要发育三角洲及滨浅海沉积体系,储层岩石类型以岩屑石英砂岩、长石岩屑砂岩为主,砂岩颗粒呈圆状、次圆状,常见点—线接触,具备中—低结构成熟度特征;②储层物性为中—低孔隙度、低渗透率,储集空间以粒间溶孔和粒内溶孔为主,其次为晶间溶孔、铸模孔和杂基微孔;③沉积作用是储层物性的主控因素之一,有利储层发育于三角洲前缘水下分流河道和河口坝微相,以及滨海相的临滨砂坝和浅滩微相区域;④压实作用与局部高钙质胶结导致储层物性变差,溶蚀作用可以在一定程度上改善储层物性;⑤处于三角洲前缘水下分流河道微相与滨海相临滨砂坝微相区域的B3-8、B3-6区为有利储层发育区,处于三角洲前缘河口坝微相区域的BX-1E区为次有利储层发育区。

In order to make clear physical property, origins of low-permeability reservoirs, and favorable reservoir distri bution, as well as to provide geological basis for comprehensive evaluating later hydrocarbon accumulation and optimal selecting potential exploration and development targets, this study took Lingshui Formation, Baodao area, Qiongdongnan Basin, as an example, and systematically analyzed the petrology, physical property, reservoir space characteristics, and the main factors affecting physical property by means of some data on well logging, cast thin section, SEM observation, clay X-ray diffraction. And accordingly, several favorable reservoir development belts of Lingshui Formation were defined. Results show that (1) two depositional systems of deltaic and littoral-neritic marine are mainly developed in Lingshui reser voirs, which are dominated by lithic quartz sandstone and feldspathic litharenite. Sandstone grains are mainly in the shape of round and sub-round and contact chiefly in the form of point and line, with the characteristics of medium- to low-tex ture maturity;(2) Linshui reservoirs are of medium to low porosity and low permeability, and their space is dominated by intergranular and intragranular dissolved pore and secondarily by intercrystalline dissolved pore, moldic pore, and matrix micropore;(3) sedimentation is one of the main factors controlling physical property. Favorable reservoirs are developed in the underwater distributary channel and mouth bar microfacies of deltaic front facies and in the shoreface sand bar and shoal microfacies of littoral facies;(4) both compaction and local high-calcitic cementation may make the physical property get worse but to some extent denudation may improve the physical property;and (5) located in the underwater distributary channel microfacies and in the shoreface sand bar microfacies, B3-8 and B3-6 zones are the most favorable for reservoir development, and more favorable for BX-1E zone located in the mouth bar microfacie.