Determination of oiygas phase in continental shale: Taking Member Chang 7 shale of Yanchang Formation in Ordos Basin for example

This paper discusses the type of the fluid oil/gas phase in Member Chang 7 continental shale of Triassic Yanchang Formation in Orqos Basin. Based on the high pressure PVT (pressure-volumetemperature) test data, the oil/gas phase diagram of Yanchang Formation oil reservoir is mapped. The phase of Member Chang 6 & Member Chang 8 oil reservoirs in the west of the basin is considered as a single oil phase and that in the east o| the basin as oil and gas phases. The oil and gas coexist in Member Chang 7 shale. According to the relationship between producing gas-oil ratio and depth of the typical Member Chang 6 & Member Chang 8 oil reservoirs and the thermal evolution of organic matter (R0) of Member Chang 7 shale, the linear relationship between the depth and R0 of Member Chang 7 oil/gas phase shale is established. Based on the depth and R0 distribution isograms of Member Chang 7 shale, the Zibei, Ansai, Xiasiwan, ijuxian areas in the east of the basin are determined as shale oil and gas phases zone. The shale gas is composed of adsorbed gas, free gas and crude oil dissolved gas. The oil/gas phase in the west of the ba^injis a single oil phase zone, mainly occurring shale oil and the gas is crude oil dissolved gas. This determined method can be applied to phase evaluation of the continental rich in organic matter shale formations being at the organic matter maturation stage (J?.,' = 0. 5%̃1. 3%).