文昌13-1/2油田珠江一段细粒储层沉积相及低阻油层性质

Geological Origin and Genesis of Low-Resistivity Oil Layers in Wenchang13-1/2 Oilfield

文昌13-1/2油田位于珠江口盆地琼海低凸起倾斜端,在珠江组一段中上部发育粉砂-泥质粉砂细粒海相沉积储层。近来发现该层段含油丰富,主力低阻油层地质储量可观。通过对岩心、测井、地震等资料的综合分析表明,该区的沉积环境主要为浅海陆棚,低阻油层主要发育于下临滨及滨外砂坝沉积微相,局部发育风暴砂。该类低阻油层泥质含量高,电阻率绝对值相对低,与常规油层相比具有高孔低渗的物性特征。通过成因机理探讨,确定了高束缚水饱和度和附加导电能力较强的黏土矿物(伊蒙混层、伊利石)是该区低阻油层发育和分布的主控因素。这类海相低阻油层在我国油气勘探史上尚属首次出现,深入探讨该区细粒储层沉积特征及低阻油层特征对今后及时发现和高效开发此类油田具有重要意义。

Wenchang 13-1/2Oilfield is situated in the Qionghai low uplift of Pearl Mouth Basin,and the upper part of ZJ1 member is characterized with marine fine siltstone and muddy siltstone.Recently,this member has been found abundant in oil and also geological reserves in the main low-resistivity oil layer（LROL）.The comprehensive measures of cores and logging as well as seismic analysis show that shelf sea is the main depositional environment of this area,and shoreface bar and offshore bar are the main low-resistivity oil layer sedimentary microfacies belt,which are deposited by storm.The low-resistivity reservoir has high shale content.The reservoir has relatively low absolute resistivity value and the characteristics of high physical property of low permeability compared with conventional reservoirs.The genesis mechanism analysis reveals that high irreducible water saturation and clay minerals with strong conductive ability（andreattite,goeschwitzite）are the main controlling factors of the development and distribution of the low-resistivity oil layer in this area.This kind of marine low-resistivity oil layer is found for the first time in China.Understanding the fine reservoir sedimentary features and the low-resistivity reservoir characteristics in this area is of great significance in discovering and efficient development of such fields in future.