Principle and Application of Distinguishing Oil-Water Contact in Complex Architectural Units Based on Pressure Gradient Method

Pressure gradient method is based on the principle of connectedness, using formation pressure test data to character pressure gradient curves of reservoir fluids and distinguish oil water contact. The greatest advantage of this method is Intuitive identification of oil and water contact depth. It provides basis for fine reservoir description and progressive exploration and development. According to the data of single well test, the regional water pressure curve is fitted. The difference between the hydrostatic pressure curve and the hydrostatic pressure curve is defined as the overburden pressure. The depth of test point and test pressure, formation water density and crude oil density are established to calculate the depth of oil-water contact. Well Che 47 Block, because of many times of vertical volcanic cycle, complex lithology and lithofacies, and strong heterogeneity of secondary reservoirs, multiple lithologic shielding bodies can be identified. By using the pressure gradient method and combining the reservoir geological characteristics of the industrial area, it is revealed that at least 3 relatively independent reservoir units in the Well Che 47 Block, and the corresponding depth of oil-water contact is −2786 m, −2848 m and −2912 m respectively. According to the relationship between the depth of the oil and water contact and the position of the test point, it is conservative to predict that the lowest oil layer is at least 200 m of the oil column height, and the prospect of rolling is good. The application of the pressure gradient method to identify the oil-water interface in complex reservoirs is more in line with the actual underground conditions. This method, combined with seismic and log data, can provide an important basis for the fine evaluation of complex volcanic reservoirs.