酸压动态条件下酸岩反应动力学参数测试新方法

A New Method of Measuring Acid Rock Reaction Kinetics Parameters under Dynamic Conditions

酸压中活酸作用距离是评价酸压效果的重要因素。活酸作用距离取决于酸岩反应速度,酸岩反应动力学参数是酸压优化设计基础,这些参数的准确性决定优化设计的可靠性。设计了一种测试动态条件下裂缝中酸液有效传质系数和有效消耗时间的新方法,该方法通过酸蚀裂缝导流驱替实验,测试酸化前后岩板质量变化;基于岩板质量变化计算酸液消耗速度、酸液有效传质系数,再基于裂缝中的酸液量和酸液消耗速度计算酸液有效消耗时间。采用延长马家沟组岩板测试了稠化酸和交联酸的反应动力学参数,交联酸比稠化酸黏度高,有效传质系数比稠化酸低,在使用的实验条件下,稠化酸和交联酸在裂缝中的有效消耗时间分别为20 min和28 min左右。研究为酸压优化设计和酸液体系评价提供了依据。

Live acid penetration distance in acid fracturing is an important factor in acid fracturing effect evaluation. Live acid penetration distance depends on acid rock reaction rate. Acid rock reaction kinetics parameters are basic data in acid fracturing designs. The accuracy of these parameters determines reliability of the designs. This paper designed a new method to measure effective mass transfer coefficient and effective acid consumption time under dynamic acid fracturing conditions. This method makes use of acid fracturing conductivity flooding experiment to measure mass variation of core slabs before and after flooding, based on which acid consumption rate and acid mass transfer coefficient are calculated. Then effective acid consumption time is calculated in terms of the acid volume and acid consumption rate. This paper measured kinetics parameters of crosslinked and gelled acids with core slabs from Majiagou formation of Yanchang field. The crosslinked acid has a higher viscosity and lower mass transfer coefficient than the gelled acid. Under the conditions used in this paper, the gelled acid and crosslinked acid have an effective consumption time of about 20 and 28-minute respectively. This study provides basis for acid fracturing optimization designs and acid system evaluation.