Solid Phase Deposition Pattern Concerning Formation Oil in YD 7 Reservoir of Tarim Oilfield and Its Application: A Case Study

Abstract

Yudong (YD) 7 reservoir in the Yingmaili area of Tarim Oilfield is one of the key areas of oil and gas exploration in the Tarim Basin. However, due to the serious plugging problem caused by solid phase precipitation particles such as wax and paraffin, it is necessary to study the well flow phase behavior and solid phase precipitation law of typical high-production wells in this block to obtain the phase enveloping line and provide theoretical support for preventing solid phase precipitation of formation crude oil. In this study, the PVT tester and the self-designed microscopic solid deposition tester are used to obtain the phase enveloping line of formation crude oil, and the change law of the “gas–liquid–solid” phase behavior when the formation crude oil changes with temperature and pressure is observed. The morphological process of solid precipitation is recorded and analyzed through a microscopic visualization window. Finally, the solid phase precipitation point of formation crude oil is verified using a laser solid phase deposition tester. The experimental results show that under atmospheric pressure, the solid phase precipitation temperature point of surface crude oil is 34.05 °C, the maximum instantaneous precipitation is 0.01178%, and the maximum cumulative precipitation is 8.34%. The solid phase precipitation point of formation crude oil changes under different temperatures and pressures. Under different pressures and temperatures, it shows multiphase changes such as liquid–solid, liquid phase, gas–liquid–solid, gas–liquid, and gas phases. Limited by equipment, we can only observe the first four phase behaviors in the laboratory. In the process of solid phase precipitation, formation crude oil shows a fine needle shape at the initial stage and finally adhesions and aggregations in the form of an increasing crystal nucleus as the center, thus blocking the formation or wellbore. Combined with the analysis of production data, it can be seen that there is a solid precipitation problem in well YD 702 over 1200 m in the wellbore and the solid phase precipitation problem from the wellbore to the surface pipeline. This study provides theoretical support for preventing solid phase precipitation in the YD 7 reservoir and provides a reference for other oil fields with solid phase precipitation blocking problems.