深部煤层气井胍胶返排液回用处理技术优化及应用

Optimization and application of treatment technology for guanidine gum fracturing flowback fluid in deep coalbed methane wells

以胍胶为代表的水基压裂液广泛应用于深部煤层气开发,在获得高产的同时也产生大量的压裂返排液,因此开展胍胶压裂返排液回用处理技术优化、不断提高返排液的回用率具有重要意义。为解决胍胶压裂返排液回用处理存在的破胶不彻底、有害离子去除难等技术难题,通过破胶参数优化实验,分析添加剂对破胶的影响,并采用光谱分析和响应曲面法(RSM),探索胍胶压裂液在深部煤层气井高温环境及返排过程中的破胶机理和最佳工艺条件,从而为胍胶聚合物在地层实现"完全"破胶处理工艺提供理论依据。通过有害离子交互作用实验,并结合冗余分析法(RDA)分析残余在返排液中不同离子间的交互作用,以及对压裂基液配制、压裂液性能的影响,从而获得不同离子对配液回用的影响规律与最佳控制指标。在此基础上,提出胍胶压裂返排液回用处理工艺设计,并在应用中进行验证。结果表明:破胶液的黏度和残渣含量分别与破胶剂浓度、破胶温度和破胶时间符合二次多项式回归模型,在破胶剂浓度为0.03%、破胶温度为91℃、破胶时间为2.9 h时,可获得破胶液黏度和残渣含量最低值,这对指导压裂生产和返排液破胶降黏具有重要指导意义;明确了返排液中B、Al^(3+)、Fe^(3+)、Na^(+)、K^(+)、Ca^(2+)、Fe^(2+)7种主要离子对压裂液基液性能、对交联后压裂液性能的影响顺序,通过调整不同离子浓度组合,可获得最佳性能的压裂基液和压裂液,用于指导胍胶压裂返排液回用处理时各离子浓度控制;采用"破胶降黏+混凝+气浮+定向去除+过滤+除硼"优化工艺处理胍胶压裂返排液,出水满足配制水质指标要求,所配制的压裂液性能满足水基压裂液技术要求,回用率由40.00%提高至92.01%以上,直接处理费由120元/m3降至40元/m3,不仅减少了大量水资源消耗、降低了拉运频次,还节约了开发成本、降低了安全环保隐患。

Water-based fracturing fluids,represented by guanidine gum,are widely used in the development of deep coalbed methane,a large amount of fracturing flowback fluid is generated while achieving high yields.It is of great significance to optimize the treatment technology for guanidine gum fracturing flowback fluid and continuously improve the recycling rate of flowback fluids.This study aims to address technical challenges in the recycling treatment of guanidine gum fracturing flowback fluid,such as incomplete breaking of the polymer and the difficulty in removing harmful ions.It has proved the effect of additives on polymer breaking through polymer-breaking parameter optimization experiments;using spectroscopic analysis and response surface methodology(RSM),it explores the mechanism of polymer breaking and the optimal process conditions for guanidine gum fracturing fluids under high-temperature environments during flowback in deep coalbed methane wells.This provides a theoretical basis for achieving the complete breaking of guanidine-based polymer in reservoirs.Through the experiments on the interaction of harmful ions in combination with redundancy analysis(RDA),the paper analyzes the interaction of residual ions in flowback fluids,as well as their effects on the formulation and performance of fracturing fluid,thus determining the influence patterns and optimal control indicators of different ions for fluid recycling.On this basis,the study proposes a design for the recycling treatment process of guanidine gum fracturing flowback fluid which is validated in practical applications.The results indicate that the relationship between the viscosity and residue content of breaking agent and the concentration of breaking agent,breaking temperature,and breaking time is in conformity with quadratic regression models.The lowest viscosity and residue content can be achieved at the breaking agent concentration of 0.03%,and 91℃for 2.9 h.This has great significance for guiding fracturing production and reducing the viscosity of flowback fluids.The study also establishes the sequence of the major ions(B,Al^(3+),Fe^(3+),Na^(+),K^(+),Ca^(2+)and Fe^(2+))in flowback fluids that affect the properties of fracturing base fluids and crosslinked fracturing fluids.By adjusting the concentrations of different ions,the base fluid and fracturing fluid with optimal performance can be obtained,which can guide the control of ion concentrations during the recycling of flowback fluids during guanidine gum fracturing.After optimizing the treatment process of"polymer breaking and viscosity reduction+coagulation+air flotation+selective removal+filtration+boron removal,"the flowback fluids can meet the quality requirements for water preparation,and the properties of the prepared fracturing fluids meet the technical requirements for water-based fracturing fluids.The recycling rate has increased from 40.00%to over 92.01%,and the direct treatment cost has decreased from 120 yuan/m3 to 40 yuan/m3.This not only reduces water resource consumption and transportation frequency,but also saves development costs,lowers safety and environmental risks.