鄂尔多斯盆地临兴神府区块致密砂岩气低温压裂液优化与应用

针对鄂尔多斯临兴神府区块低温储层开展压裂液优化研究，通过大量岩心实验和测井数据认识区块储层特性，开展破胶剂体系优化实验，利用低温催化剂实现低温下快速破胶，从而实现快速返排，减少压裂液与地层的接触时间。同时，利用30~80 ℃高活性生物酶破胶剂，高效降低破胶液残渣含量，实现残胶的彻底清理，从而保证裂缝的导流能力。各种破胶剂加量的设计考虑压裂液注入对地层温度的影响，进行阶梯化设计，实现较短时间破胶。针对储层物性特征对稠化剂、黏土稳定剂和助排剂等进行优化，得到一套经济有效的压裂液体系。该体系在本区块30多口生产井约100层应用，统计现场测试基液黏度为18~27 mPa · s，交联时间35~55 s。压裂施工结束关井1 h后，开井放喷，返排液黏度均低于5 mPa · s，已完全破胶。初期产量和累计产量均明显好于采用压裂液体系未经过针对性设计的单一氧化性破胶剂，且多口井实现高产，证明优化后的压裂液体系在该区块具有非常好的适用性。

Optimization of low-temperature fracturing fluid and its application in the tight sandstone gas in the Linxingshenfu Block of the Ordos Basin

A series of studies were carried out to optimize the fracturing fluid to be used in the low-temperature reservoirs in the Linxingshenfu Block of the Ordos Basin. After the reservoir characteristics were understood based on a great number of core experiments and logging data, experiments were carried out on the gel breaker system for its optimization, and low-temperature catalyst was adopted for fast gel breaking under low temperature, so as to realize fast flowback and reduce fracturing liquid-formation contact duration. Meanwhile, the gel breaker of 30?80 ℃ high-activity biological enzyme was adopted to reduce the content of residual gel breaker efficiently so as to realize the thorough removal of residual gel and ensure the flow conductivity of fractures. Considering the effect of the injection of fracturing fluid on the reservoir temperature, the dosages of various gel breakers were designed in the stepwise mode so as to realize the gel breaking in a shorter time. Then, thickener, clay stabilizer and cleanup additive were optimized based on the reservoir physical properties. And thus, a set of economic and efficient fracturing fluid system was prepared. This system has been applied in 100 layers in over 30 production wells of Linxingshenfu Block. It is shown that the base fluid has the viscosity of 18?27 mPa · s and the crosslinking time of 35?55 s. After the fracturing is completed, the well is closed for 1 h and then opened for flowing, when the viscosity of flowback fluid is 5 mPa · s, indicating complete gel breaking. Its initial production and cumulative production are obviously higher than those of simple oxidizing gel breaker which is not designed specifically, and many wells present high yield, proving that the optimized fracturing fluid system is well applicable in the Linxingshenfu Block.