Font Size: a A A

Research On Sequence Stratigraphy Of Middle Permian In The Western Sichuan Basin

Posted on:2013-09-14Degree:MasterType:Thesis
Country:ChinaCandidate:J G WangFull Text:PDF
GTID:2230330374976564Subject:Paleontology and stratigraphy
Abstract/Summary:PDF Full Text Request
In West Sichuan, hydrocarbon exploration and research in the previous stage mainly focused on middle-shallow continental reservoirs, and has acquired substantial achievements. However, the exploration of marine reservoirs in West Sichuan relatively lagged behind. Lacking of adequate research has become the main factor restraining the exploration of marine reservior in this region.Being guided by carbonate rock sedimentological and sequence stratigraphical theories, the study aims to trace and determine the regional sequence boundary of the Middle Permian Formation in West Sichuan, based on the observations on outcrop profiles and description of under-bore cores, in combination with comprehensive elaboration on seismic and logging data; and through single-well and link-wells tratigraphic sequence analysis, to establish the stratigraphic sequence framework for this region. Through in-depth study on the carbonate sedimentary systems and other micro-facies characteristics, the pattern of regional sedimentary facies was determined. Based on this pattern, the lithofacies paleogeographically spatio-temporal distributions of the main sequences within the framework were also studied, to illuminate the spatial distribution patterns of the key reservoir stratas and to point out the favorable reservoir facies belts, thus, providing theoretic evidence for the prediction of reservoir distribution and the exploration of large-scaled oil-gas fields in this region.The results of field investigation and under-bore core observation showed that there were two genetic types for the sequence boundary of Permian marine reservoirs: consequentially, the uplift erosional unconformity and the lithology-lithfacies transitional boundary. By using present filed seismic profile, under-bore core observation, loggin and seismic data and etc., and employing the classic sequence stratigrahpic theories, Permian formation was divided into one Grade II sequence(SSQ1) and five Grade III sequances (SQ1-SQ5). Each of the sequences was further divided into the transgressive system tracts (TST) and the high-stand systems tract(HST). On this basis, a cross-sectional comparison on the sequence of Leikoupo formation was conducted, to establish the sequence stratigraphic framework of Permian formation in West Sichuan.Through analysis on the various facies marks, such as rock type, sedimentary structure and etc., the Middle Permian formation was classified as a gentle slope-type sedimentary system. Its sedimentary facies were categorized into two main types: inside the gentle slope and inside the gentle slope. Partial region was broad tidal. The main sub-types were:tidal flat, micrite, micritic bioclastic limestone and etc. By elaborating the characteristics of the various sedimentary facies, the pattern of sedimentary facies of middle permian was determined, i.e., the gentle slope pattern.From the above, the study further analyzed the characteristis of sedimentary facies and lithofacies distribution within the sequence framework. This paper was the first to use systems tract as the mapping unit, compiling paleogeographic maps for the lithofacies of various reservoir strata within Permian formation. According to the paleogeographic characteristics of lithofacies at the various sequences, in combination with the investigation on conformation patterns of the previous and contemporaneous tectonics maps for the subject area, the paleogeomorphological evolution pattern of this region was elaborated. During SQ1-SQ5period, Permian formation generally depicted a trend of "shallow in south and east, deep in north and west", illustrating a paleogeomorphological pattern of "lower in north and west, higher in east and south". The study area development shallows sedimentary, which was advantageous of the development of shallows type reservoir. Considering property data characteristics for reservoirs at different periods, a comprehensive investigation on the reservoir strata within the subject area was performed, to draft a prediction that the sequences worthy of emphasized exploration within Permian formation were:SQ2and SQ3.
Keywords/Search Tags:The western of Sichuan basin, Middle Permian formation, SequenceStratigraphy, Sedimentary facies, lithofacies paleogeography, Favorable reservoir faciesbelt
PDF Full Text Request
Related items