Simulation and Production Optimization on Enhanced Oil Recovery during the Middle and Late Period for SAGD Development in Ultraheavy Oil Reservoirs with Interlayers

Xiaokun Zhang,Xuan Du,Pengcheng Liu,You Zhou,Zhaojie Song

doi:10.1155/2022/3474741

Abstract

Previous studies on the technique for using the remaining oil are incomplete and inaccurate according to the position of the interlayer of the Steam-Assisted Gravity Drainage (SAGD) technique, and comparative studies of infilled horizontal wells are lacking. In this study, the SAGD well pair in the superheavy oil reservoir in the Z block in the Xinjiang Oilfield, China, was taken as an example. According to the reservoir’s geological parameters and production parameters, a typical well group geological model was created for the first time. The model divided the well groups in block Z into three categories according to the position of the interlayer, the production degree of the horizontal section, the oil recovery ratio, and the available degree of reserve control. According to the geological classification results, different typical well groups without an interlayer, with an interlayer located above the steam injection well, and with an interlayer located between the well pairs were classified and analyzed using numerical simulations. This was the first time the infilled horizontal well technique was compared with the infilled vertical well-assisted SAGD technique. In addition, the steam chamber connection law of the infilled vertical well-assisted SAGD was clarified. The results show that for reservoirs without an interlayer, the use of infilled horizontal well-assisted SAGD could speed up the lateral connection of the steam chambers and reduce the residual oil saturation. For reservoirs with a low production degree in the horizontal section and that are affected by an interlayer, an infilled vertical injector could be used with the assisted SAGD technique to increase the oil recovery by 5%–13%. The results of this study provided strong guidance for the next step in using enhanced oil recovery techniques to achieve traditional SAGD production from superheavy oil reservoirs with an interlayer.

Highlights

Steam-Assisted Gravity Drainage (SAGD) is a key technique for the development of ultraheavy oil, which has been widely used in Alberta, Canada, and the Xinjiang and Liaohe oilfields in China
(1) For oil reservoirs without interlayers, the method of using infilled horizontal wells between the SAGD well pair can speed up the lateral connection of the steam chamber, reduce the residual oil saturation, increase the final recovery rate, and reduce the steam to oil ratio
Using the infilled horizontal well located above the interlayer for steam injection can increase the oil recovery by 6%; the infilled horizontal well can increase the oil recovery factor to a limited extent

Summary

Introduction

Steam-Assisted Gravity Drainage (SAGD) is a key technique for the development of ultraheavy oil, which has been widely used in Alberta, Canada, and the Xinjiang and Liaohe oilfields in China. According to the actual production situation of the oilfield, as an ultraheavy oil reservoir with interlays enters the late stage of development, the differences in the reservoir conditions are enhanced and the reservoir’s heterogeneity is increased, resulting in a prolonged SAGD production cycle and decreases in the oil-gas ratio and economic returns. Many researchers have studied the effect of reservoir heterogeneity on SAGD recovery through experiments and numerical simulations [3,4,5,6,7,8,9,10,11,12].

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Conclusion