Session: 11-10-03 Development of Unconventional Reservoirs-3

Paper Number: 79022

79022 - Experimental Study on the Influence of Hydraulic Fracturing on Hydrogen Sulfide Generation in Longxi Block of Daqing Oilfield 

Hydraulic fracturing has a significant effect on increasing production and injection in oil and water wells in low permeability dense reservoirs. H₂S gas is generated after hydraulic fracturing in oil and water wells in Longxi Block of Daqing Oilfield, and the highest value of H₂S content in casing gas has reached 232 ppm, which exceeds the safety critical concentration value (20 ppm), increasing the risk and difficulty of production and operation construction. In order to reveal the mechanism of the effect of fracturing on H₂S generation in Daqing oilfield formations, this study conducted experimental simulations of the TDS, TSR and bioreduction reaction of SRB with different compositions of fracturing fluid. The results show that the fracturing fluid composition affects the formation H₂S generation mechanism differently when the formation temperature is different. The critical temperatures for TDS and TSR reaction in the formation are 100℃ and 140℃, respectively, and the higher the temperature, the higher the amount of H₂S is generated. Potassium persulfate and sodium sulfite in the fracturing fluid can promote the amount of H₂S generated from TDS and TSR reaction, but does not change the critical reaction temperature of TDS and TSR reaction. SRB exists in the formation of Longxi block, and guar gum and sulfur-containing materials in the fracturing fluid can provide nutrition for SRB when the formation temperature is not higher than 56℃, which promoted the rapid reproduction of SRB in a short period of time, and then generated a large amount of H₂S. The mechanism of H₂S generation for fractured wells in the Longxi block at temperatures of 30~56°C is the proliferation of SRB in the fracturing fluid. The mechanism of H₂S generation in fractured wells at temperatures of 100~120°C is that sulfur-containing materials promote TSR reaction. This study clarified the reasons and conditions for the generation of H₂S, and played an important role in the subsequent research on H₂S prevention and control measures.

Presenting Author: Hongyu Sun China University of Petroleum Beijing

Authors:

Hongyu Sun China University of Petroleum Beijing
Liguo Zhong China University of Petroleum Beijing
Jianbin Liu China University of Petroleum Beijing
Tongchun Hao China University of Petroleum Beijing
Shihao Li China University of Petroleum Beijing
Yu Zhu China University of Petroleum Beijing
Hailong Zhang Downhole Operation Company of Daqing Oilfield Co Ltd
Kexin Wang Downhole Operation Company of Daqing Oilfield Co Ltd