Application of mathematical geology methods to analysis of the sedimentary facies of sandstone reservoir: An example of the reservoir of the neogene in Huatugou Oilfield, Qaidam Basin

Abstract

The analysis of the sedimentary facies of the reservoir is important for the exploration and development of one oilfield. And obvious types of facies symbols which are macro and micro are necessary to the division of the sedimentary facies. During the study of the sandstone reservoir of the Neogene in Huatugou oilfield, Qaidam Basin, on the basis of the general columnar section of the Neogene in Huatugou oilfield and the data of 2 systemic wells and 12 exploration wells, the authors have obtained some macro facies symbols helpful to divide the sedimentary facies with the Markov chain analysis and time-trend analysis, such as the cycles of the lithologic variation and the main types of the rhythm and its assemblage. Conjoint with the color, the laminations, the deformation structures, the types of the carbonate rocks and the special sediments, the authors analyzed the sedimentary facies of the Neogene reservoir in Huatugou oilfield. It is concluded that (1) it is a important assistant means of ascertaining the key beds of an exploration well to obtain the cycles of the lithologic variation with Markov chain analysis; (2) main deposits and main modes of the lithologic transference obtained by time-trend analysis are helpful to ascertain the hydrodynamic condition and the evolvement process of sedimentary environment; (3) the main types of the sedimentary facies of the Neogene in the Huatugou oilfield include braided channel deltaic plain, deltaic frontal margin, fore-delta, littoral lake and shallow lake facies.