Abstract:

Whether wellhead Construction pressure could be effectively reduced is the bottleneck of restricting the safe and efficient development of deep tight or ultradeep reservoir with abnormal fracture pressure. Acid pretreatment is an effective method of decreasing formation fracture pressure. But for a specific formation, acid type, acid concentration, acid strength of acid pretreatment and how much the fracture pressure can be reduced after acid pretreatment often depend on experience, and theoretical guidance is badly required. In this paper, a sandstone acid injury model is established through analysis of changes in rock mechanical properties caused by acid pretreatment, and the value of fracture pressure is quantitatively calculated after acidification on the basis of the injury model. Through the comparison of the decreased fracture pressure of two wells before and after the acidification and the simulation results, the model can be regarded as to be reasonable and can be used to guide the onsite acidzing operation, decrease operation risks. This study has important significance and reference value for promoting theoretic development of hydraulic fracturing in deep reservoir.

Key words: acidzing pretreatment, fracture pressure, injury model, rock mechanical parameter, quantitative calculation