Sand Body Microfacies Types and Single Sand Body Division in Sandy Braided River Reservoirs: A Case Study from Yan10 Member in the H303-6 Well Area, Southwestern Ordos Basin, China

Abstract

This paper takes lower Jurassic Yan10 Member of the H303-6 well area as an example in southwestern Ordos Basin. Beginning with core, well logging, logging and other data, mainly using lithology and sedimentary structure and other sedimentary facies indices, combined with logging curve characteristics, it is firstly considered that the Yan10 Member belongs to sandy braided river facies, and main sand body microfacies types of sandy braided river of Yan10 reservoirs are recognized in the study area. The key point of this paper is to identify together single sand body by core, logging curve and sand body microfacies. By using “microfacies profile genetic analysis method”, sand body is mainly divided into “central bar single sand body”, “channel sand single sand body”, “channel margin single sand body”, “river flat single sand body” and so on in Yan10 reservoirs. Depending on the characteristics of well logging response, the vertical contact style of single sand body is mainly consist of “isolated style”, “overlap style” and “overlay cutting style”, while the lateral contact relation mainly includes “butt-joint type” and “side shear type”. The distribution characteristics of single sand body are analyzed by contact relation pattern of sand body. According to well pattern type, injection-production well groups are divided, and the injection-production correspondence between water injection well and oil well is judged. By identifying the connectivity of single sand body, injection and production relationship types are divided into “injection and production type”, “injection and no production type”, “production and no injection type” and “no production and no injection type”. Based on the distribution characteristics and connectivity of single sand body, specific measures of injection and production improvement are proposed to provide a reliable basis for timely adjustment of reservoirs development plan. The division of single sand body is a very important work of this research.KeywordsCentral barChannel sandSandy braided riverSedimentary microfacies of reservoirsSingle sand body division