济阳坳陷泥质岩油气藏类型及分布特征

OIL-GAS ACCUMULATION TYPES AND DISTRIBUTION OF MUDSTONE ROCKS IN THE JIYANG DEPRESSION

济阳坳陷目前已发现的泥质岩油气藏主要分布于东营凹陷和沾化凹陷的断裂、断鼻构造带附近,依据其储集空间可分为裂缝型、孔隙型及孔—缝复合型3种类型。其中,裂缝型油气藏占主要地位,主要发育于富钙质的脆性泥页岩中;孔隙型油气藏主要发育于含砂质条带的欠压实泥岩中;孔—缝复合型油气藏发育于钙质泥-页岩互层且夹薄层砂质条带的岩类中。泥质岩油气藏以自生自储为主,需要富钙质或欠压实等特定的岩性条件,一般发育在断裂活动带附近。横向上,裂缝型油气藏主要分布于厚层生油层中富钙质高阻层段,尤其是页岩发育的薄互层段,孔隙型油气藏只分布于具有断裂或隆起背景且富含砂质条带的欠压实区;纵向上,泥质岩油气藏主要分布于2200m以下的沙河街组四段上亚段、沙河街组三段下亚段及沙河街组一段下亚段等层位。

Mudstone reservoirs discovered so far in the Jiyang Depression is mainly distributed around the faulting and nose-like structures in the Dongying Sag,Zhanhua Sag and so on. According to the storage space, three types could be classified：fissure type, pore type and pore-fissure compound type oil-gas accumulations. The fissure type one was predominates and mainly developed in brittle and calcium-rich mudstones and shales. The pore type one occurred mainly in undercompacted and sandy strip-bearing mudstones, and the pore-fissure compound type one developed in the rocks of calcium mudstone-shale interbeds with partings of lamella sandy strips. The mudstone reservoirs were characterized mainly with self-generation and self-storage,which needed some special lithological conditions such as abundant calcium or under-compaction, etc., and distributed generally near the active fault zones, nose-like structures and fault-uplift structures. Laterally, the fissure type oil-gas accumulations distributed mostly in the thick matured hydrocarbon source rocks with rich calcium and high electrical resistivity, especially in the thin interbeds with well-developed shale. The pore type oil-gas accumulation distributed only in the under-compacted region with rich sandy strips on the background of faulting or fault-uplift structures. Vertically,the mudstone reservoirs distributed mostly in the layers of well depth below 2 200 m, which were the strata of the upper sub-member of Member 4, Shahejie Formation, the lower sub-member of Member 3, Shahejie Formation and the the lower sub-member of Member 1, Shahejie Formation.