Establishment and Application of a Pattern for Identifying Sedimentary Microfacies of a Single Horizontal Well: An Example from the Eastern Transition Block in the Daqing Oilfield, Songliao Basin, China

Abstract

The study of sedimentary microfacies of horizontal wells is important for improving oil recovery using horizontal well technology. Vertical well data alone do not provide accurate enough information to determine the sedimentary microfacies of horizontal wells. Therefore, a comprehensive method combining the data of both horizontal and vertical wells was established to identify sedimentary microfacies of horizontal wells and applied to a single horizontal well in the Daqing oilfield in China’s Songliao Basin. The results identified the study area as a delta sedimentary environment, mainly subdivided into four microfacies types: a distributary channel, the main overbank sand, the overbank sand, and an interdistributary bay. The criteria for identifying each sedimentary microfacies were established. Among them, the criteria for identifying distributary channels include a natural gamma value continuously less than 90 API; a resistivity value continuously greater than 11 Ω·m; a logging curve, which is typically bell-shaped or box-shaped with very high amplitude and amplitude difference; a mainly siltstone lithology; and a total hydrocarbon content (Tg) continuously greater than 3%. The variations in the two types of channel boundaries (narrowing of the channel boundary and reverse extension of the bifurcated channel boundary) were corrected. The research results can provide guidance for the efficient development of favorable reservoirs in oilfields using horizontal well technology.