微胶囊包裹化学生热压裂液破胶技术

低温浅层油气井的压裂,常由于低温下常规破胶剂活性太低而破胶困难。为避免这类问题的出现,可采用微胶囊包裹化学生热压裂液进行压裂。从化学生热体系的筛选、草酸微胶囊的制备及评价、微胶囊包裹化学生热剂与常规水基压裂液的配伍性等几个方面对用于低温浅层油气井的微胶囊包裹化学生热压裂液体系进行了研究。通过试验,选定NH4Cl-NaNO2生热体系,并根据其反应特点,对该体系的催化剂草酸,利用相分离法进行微胶囊包裹。当NH4Cl-NaNO2-草酸微胶囊与羟丙基瓜尔胶压裂液复配后,体系的稳定性及抗剪切性能都保持较好。结果显示,当体系初始温度为30℃、NH4Cl和NaNO2浓度为2.0 mol/L、草酸微胶囊质量分数为0.93%、过硫酸铵质量分数为0.93%时,170s-1剪切速率下连续剪切2h后,压裂液黏度能保持在300 mPa·s左右,生热峰值温度能达到78℃,4h后破胶液黏度为3.12 mPa·s。另外还对该压裂液的压裂工艺进行了阐述。

New Hydraulic Fracturing Fluid with Microencapsulated Heat -Generating System

During fracturing of low-temperature, shallow oil and gas reservoirs, it is difficult to break viscosity because of low activity of convention viscosity breaker at low temperature. To avoid those problems, a new microencapsulated heat-generating hydraulic fracturing fluid system was proposed. Studied the select for chemical heating system, prepare and evaluate oxalate capsule, heat generate of micro-capsule packing chemical and compatibility of conventional water base fracturing fluid. From experiment, NH4Cl-NaNO2 system was selected as chemical heat-generating system. According to reaction characteristics of this system, oxalic acid is chosen as catalyst of reaction and encapsulated using ethyl cellulose and paraffin as coating materials by phase separation method. Compounding with oxalic acid microcapsule, gel-breaker and 2.0 mol/L heat-generating agents, its final viscosity keeps to about 300 mPa·s when it is sheared at the rate of 170 s-1 in 2 hours,and after 4 hours, the viscosity of breaker is 12 mPa·s. And corresponding fracturing technology also is discussed here.