海相断陷盆地输导体系分类及组合模式特征:以琼东南盆地古近系陵水组为例

以琼东南盆地古近系陵水组为例,针对海相断陷盆地钻井资料少、地震资料复杂、断裂体系发育、地层破碎、有利勘探目标预测难度大等问题.在Vail经典的层序地层学理论指导下,基于浅水区钻井资料和深水区地震资料,井震资料紧密结合建立研究区目的层三维等时地层格架,将目的层划分为层序I、层序Ⅱ、层序Ⅲ和层序Ⅳ4个三级层序.岩石类型、沉...

Classification and combination model characteristics of pathway system in marine faulted basin:Taking the Paleogene Lingshui Formation,Qiongdongnan Basin as an example

Taking the Lingshui Formation of the Paleogene in the Qiongdongnan Basin as an example, the problems associated with oil and gas exploration include limited drilling data, complex seismic data, development of fault system, and difficulty predicting favorable exploration targets. In this study, under the guidance of the classical sequence stratigraphy theory of Vail, we established the isochronal stratigraphic framework by closely combining the shallow water drilling data with the deep water seismic data in delineating the target strata into four three-level sequences. Evidences from rock types, sedimentary structures, authigenic minerals and biological fossils showed that the target strata formed in a marine sedimentary environment. In the isochronous stratigraphic framework, we carried out the single element analysis for each geogenetic pathway system through sediment analysis, fault system interpretation, and unconformity characterization. The pathway system of the target strata was genetically divided into three main types-reservoir, fracture and unconformity, and we described in detail the spatial developmental characteristics of different types of transport systems. The slope and pelvic floor fans in the lower system domain, the fan delta, beach bar and shore sand in the pathway system domain, and the fan delta and braided river delta in the higher system domain are the main sedimentary facies types corresponding to the reservoir transport system. The large controlling concave fault spreading in the northeast can be a favorable channel for oil and gas migration. The unconformity is divided into four categories: parallel, overlap, truncation and overlap-truncation unconformities. The widely developed unconformity in the sequence interface can be a favorable migration channel and plays an important role in oil/gas migration and transmission. We further analyzed the spatial combinations of different pathway systems and summed up the modes of combination into six types: fault+unconformity (reservoir) or “T” type transport, fault+unconformity (reservoir) or comb type transport, fault+reservoir or grid type transport, fault+unconformity or stepped type transport, and fracture type transport (fracture+bedding surface+pore). We then located each type of pathway system in the basin, and established the pathway system model. Based on the analysis of petroleum geological characteristics, such as temperature/pressure field and fluid potential as well as hydrocarbon source rock and cap rock, we predicted the favorable oil and gas exploration zones, which mainly included the north margin of the Yanan Depression, the Songxi Depression, the north margin of the Songnan Depression, the periphery of the North Reef Depression, the south slope of the Lingshui Depression, and the north and south margins of the Changchang Depression. Among the four sequences, sequence Ⅰ was the most favorable zone, followed by sequences Ⅲ and IV, whereas sequence Ⅱ was the least favorable zone.