Laboratory investigations of hydrous pyrolysis as ternary enhanced oil recovery method for Bazhenov formation

Abstract

Significant amount of different maturity kerogen in Bazhenov oil-shale formation are reserves of hydrocarbons to be recovered by enhanced oil recovery methods in nearest future when the conventional oil field development drops crucially. A technology of in-situ kerogen conversion into synthetic oil in Bazhenov formation opens broad perspectives in development of Bazhenov formation, West Siberia, Russia.Laboratory investigation of in-situ kerogen conversion process in the presence of supercritical water performed on Bazhenov formation rocks is presented in this study. A feasibility of the tertiary hydrous pyrolysis hydrocarbons (HC) recovery method was accessed. Study helped to obtain reliable data to validate the numerical simulation model for that enhanced oil recovery method.First tests of hydrous pyrolysis extraction were conducted on crushed oil shale samples at temperatures of 300, 350, 400 and 480 °C and under formation pressure of 30 MPa. Liquid HC extraction from sample started from 400 °C. The secondary hydrocarbons conversion process was detected at reaction temperature of 480 °C.Second stage of laboratory tests allowed to find optimal parameters for in-situ kerogen conversion – optimal conversion temperature, time of the conversion. The experiments on Bazhenov formation cores with low kerogen maturity were conducted in closed vessel at formation pressure and in temperature range of 250–400 °С. It was found that oil synthesis starts at 300 °С. Amount of liquid products increased at temperatures above 350 °С, but the secondary cracking processes had been observed also.It was discovered that hydrous pyrolysis and cracking caused an increase in rock porosity and permeability. Results obtained in this study were used in numerical simulation.