Productivity Analysis of Fuyu Oil Shale In-Situ Pyrolysis by Injecting Hot Nitrogen

Shuai Zhao,Qiang Li,Youhong Sun,Xiaoshu Lü

doi:10.3390/en14165114

Abstract

In this paper, the effect of heat injection on productivity of Fuyu oil shale during in-situ pyrolysis was studied by using heat flow coupling analysis method. It is found that fluid conducts heat transmission to the oil shale stratum mainly along the fissure formed by hydraulic fracturing. With the increase of heating time, the oil shale on both sides of fissures were effectively pyrolyzed, and the porosity of the formation increases and the diffusion range of the nitrogen to the oil shale stratum is also improved. After 200 days, the oil shale around the fractures first reaches the pyrolysis temperature, and 700 days later, the average temperature of the oil shale stratum reaches 500 °C; therefore, the whole oil shale can be effectively pyrolyzed. Productivity analysis shows that the best exploitation temperature is 500 °C. When the gas injection rate is in the range of 1.0~11.0 m3/min, different degrees of heat loss will occur, and the output is also different. The pyrolysis time reaches 100~150 days, showing the peak value of daily production, which is between 0.5~3.2 m3/day. The pressure of displacement fluid affects oil shale product recovery in in-situ pyrolysis. High pressure helps to improve the displacement efficiency of oil and gas products and increase the productivity of oil shale in-situ pyrolysis. The best acting pressure is 9.5 MPa.

Highlights

The primary reservoir of oil shale is compact and has low porosity and low permeability
Even though kerogen can be pyrolyzed after heating, the macromolecular organic matter in shale oil produced by the pyrolysis of kerogen cannot be extracted effectively because of the poor conductivity of the stratum, which leads to low effective recovery of oil shale with low oil content under the normal in-situ pyrolysis process [1,2,3]
It involves using the measure of hydraulic fracturing to create fractures in the oil shale stratum between the heated well and the mining well and pump the fracturing fluid into the fractures with ceramsites to improve the conductivity of the oil shale, increase the effective contact area of the heat transfer medium with oil shale, and increase the heat conduction rate of the oil shale [5,6,7]

Summary

Introduction

The primary reservoir of oil shale is compact and has low porosity and low permeability. The technology is applied in the in-situ pyrolysis of oil shale It involves using the measure of hydraulic fracturing to create fractures in the oil shale stratum between the heated well and the mining well and pump the fracturing fluid into the fractures with ceramsites to improve the conductivity of the oil shale, increase the effective contact area of the heat transfer medium with oil shale, and increase the heat conduction rate of the oil shale [5,6,7]. Researchers have perfected the development models and productivity prediction of conventional oil and gas resources. Several researchers, such as Wei et al

Methods

Findings

Discussion

Conclusion