A Numerical Study on Acid-Rock Reaction Law in the Mahu Heterogeneous Reservoir and Design Suggestions
In the process of horizontal well segmented fracturing in tight glutenite reservoirs,the formation break-down pressure is high and the fracturing development is difficult.The acid pretratment is applied to reduce the pump pressure,which is time-consuming with low fracturing success rate.Clarification of the mineral dissolution laws under different acidizing parameters is helpful for the optimization of acid pretreatment schemes and forma-tion breakdown pressure reduction.Based on a semi-variogram function model and vector cross product method,the acidizing model considering the mineral composition characteristics of the heterogeneous reservoir in Mahu was established to quantitatively analyze the mineral dissolution law during acid pretreatment process.The study shows that the Mahu reservoir has relatively high content of feldspar and low content of carbonates.The mud acid has a better dissolution effect,and the successful application in the field has fully demonstrated the feasibility.The acid concentration rapidly decreases,the acid action weakens,which is not conducive to lower the breakdown pres-sure.There is a turning point in the acidizing time,and simply increasing it cannot improve the acid pretreatment effect.The acid pretreatment performance can be improved by appropriately optimizing acid type and increasing acid concentration.The numerical model established in this research provides a theoretical basis for the design of acid pretreatment schemes in the Mahu tight reservoir.