Sedimentary Facies Analysis And Faceis Modeling Of Lower Devonian F4 In Zarzaitine Oilfield, Algeria

Reservoir F4 in Zarzaitine oilfield, Algeria has undergone development phases of natural energy and water injection for more than 40 years since it went on stream in 1958. Up to now, Reservoir F4 is facing such problems as unknown sedimentary genesis of reservoir rock, higher oil recovery percent, lower oil recovery rate, lower opening ratios of oil and water wells, and lower control of production-injection well pattern on original oil in place (OOIP). It is crucial that detailed reservoir geology research and modified development plan should be carried out so as to further exploit the remaining oil and to improve the production efficiency. Sedimentary facies study is one of the principal aspects of detailed reservoir geology research. The study of sedimentary facies, spatial distribution of micro sedimentary facies as well as quantitative simulation of micro sedimentary faceis can meet the targets of enhancing the well-logging interpretation precision of reservoir rock properties, improving the prediction precision of spatial distribution of reservoir rock properties and guiding the analyses of oil-water migration features and affecting factors on remaining oil distribution.The stratigraphical correlation method of Facies Controlled Cycle of genetic chronostratigraphy has been utilized to construct high resolution chronostratigraphy framework. High resolution sequence stratigraphy is the theoretic basis of this method. The method, controlled by the marker zone and spatial evolution characteristics of sedimentary facies and followed the sedimentary features of stratigraphic succession, micro sedimentary facies association, stacking pattern of genetic sand-bodies and autocycle, can be applied to correlate the 5-order chronostratigraphy. This method, implying the depositing process, is favorable for chronostratigraphic correlation of event stratification such as gravity flow.With the core, experimental data, electric facies, paleontology, based on the stratigraphic succession analysis, sedimentary structure combination, depositional texture, sandbody geometry, regional geologic setting and related depositional pattern, it is considered that F4 is a sand-rich submarine fan with point source deposited by gravity flow in bathyal sea. The mid fan is subdivided into four micro sedimentary facies of braided channel, braided channel margin, inter-braided channel and braided channel frontier and the lower fan of sheet sand and basin plain.According to relations among lithofacies, micro sedimentary facies and electric facies of cored wells, micro sedimentary facies have been determined for non-cored wells. It is considered that the rise and fall of base level result in the evolution characteristics ofsedimentary facies that the lower part consists of predominant mid-fans and subordinate lower-fans and the mid part of mid-fans without lower-fans and the upper part of dominant mid-fans along with lower-fans expanding.The modeling method of multiple steps has been utilized to construct the sedimentary models of submarine fan. Firstly, the Facies Transiton Simulation is applied to construct subfacies models; then, the Object Modeling is utilized to establish the models for micro sedimentary facies of mid fan and Indicator Kriging for micro sedimentary facies of lower fan; finally, after logical operation and processing, the whole micro sedimentary facies models have been integrated. Compared with the models from single modeling method, the micro sedimentary facies models from multiple methods are much more closer to the static perspective.