济阳坳陷高青油田水下决口水道沉积模式及其砂体内剩余油形成与富集

Sub-Sea Crevasse Channel Depositional Model and Remaining Oil Forming and Concentration in the Sand Body,Gaoqing Oil-Filed

在济阳坳陷高青油田高17断块的油藏精细描述中,发现了决口水道微相,并对其成因、沉积特征与模式、空间分布进行了对比和分析,认为决口水道是在河流及三角洲沉积体系中,由主河道于大洪水期冲裂决口后,在广阔河道间形成的具有固定路径及一定限流作用的极窄而浅的短程小型水道,其形成后对原主河流流量影响较小;与主河道沉积相比,其具有粒度细、分选稍差、含泥量稍高、层理规模小、冲刷弱、略显正旋回、储层物性略差、砂体极薄(<2.5m)而窄(<100m)等特点。通过分析水下决口水道的沉积机理,建立了渐弱消失型、分支型、末端扇型和汇入型4种沉积模式;由水下决口水道形成的小而肥的井网控制不住的或注采不完全的剩余油富集砂体,数目众多,剩余油储量非常可观,在油田挖潜及油田地质研究中具有重要意义。

In the process of fine reservoir description of the Gao-17 fault block, GaoQing oilfiled, we discovered crevasse channel microfacies, and then compared and analyzed its origin, sedimentary characteristics, depositional model, and spatial distribution. The crevasse channel is an extreme narrow and shallow short range small-size channel with fixed paths and specified metering function in wide interchannels of the fluvial-delta sedimentary system, and is formed after the main stream channel rip-up in the cataclysm period. The formation of the crevasse channel impacts the original main stream channel little. In contrast with the main stream channel, the crevasse channel presents features of fine-grained, poorly graded, high Silt content, small bedding scale, weak erosion, a little normal cycle, a little bad reservoir nature, very thin sand body （〈2.5m） and narrow （G100m）,etc. By means of analyzing sub-sea crevasse channel depositional mechanism, we established 4 depositional models including fading model, branching model, extreme fan model and affluxion model. Because the sub-sea crevasse channel is very narrow and discrete, it develops small and plenty remaining oil concentration sand body of uncontrollable well network or imperfect injector producer. And because the sand body scalar quantity is very large, reserves of remaining oil are extraordinary impressive.