Superimposition patterns of underwater distributary channel sands in deltaic front and its control on remaining oil distribution: a case study from K1q4 in J19 block, Fuyu oilfield

Abstract

Taking the fourth member of the Quantou Formation in J19 block of Fuyu oilfield as an example, single sandbodies identification was performed within composite underwater distributary channels in delta front by integrating various data including cores, logging and production performance on the basis of sedimentary micro-facies. The results show that there are four main vertical superimposition patterns of single sandbodies, including separated type, overlap-type, overlay type and substitution type, and five lateral contact patterns, including interdistributary contact, embankment contact, butt-joint, side shear and substitution type. The corresponding identification marks are also summarized. The width of single sandbody is in the range from 200-800 m and their thickness range from 4-8 m. The tops of the separated type sandbodies are rich in remaining oil. In overlap-type, overlay type and substitutional type sandbodies are different in thickness and water injection direction, thus strongly influencing remaining oil distribution. Sandbodies of interdistributary contact, embankment contact and butt-joint kinds are not interconnected laterally, thus remaining oil possibly occurring in the flanks of the sandbodies. In contrast, sandbodies of side shear and substitutional type are well connected laterally, unfavorable for enrichment of remaining oil.