Diverting Acid Used for Acidizing Tight Marlstone Reservoir
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摘要: 为解决束鹿凹陷泥灰岩致密油储层以往改造中面临施工压力高、改造距离短和导流能力低的难点,根据泥灰岩酸岩反应特征,优化了自转向酸体系配方,开展了转向酸体系黏度性能、流变性能及破胶性能评价。利用岩心流动实验方法,研究了酸液对裂缝网络的沟通作用,明确酸液体系与施工参数对酸蚀裂缝网络的影响。实验结果表明,自转向酸具有低伤害、易破胶和易均匀布酸的优点,残酸浓度降低到5%时黏度可达到96mPa²s;酸液能够实现侧向对天然裂缝的大幅度沟通,满足泥灰岩储层改造的要求。对比不同改造工艺下裂缝导流能力,形成一套适合泥灰岩储层的转向酸压与加砂压裂复合的体积改造模式,该技术在ST1H井等3口井15段中综合应用,稳定日产量是以往的10倍。Abstract: In improving the tight marlstone reservoir in Shulu sag, problems such as high operation pressure, short improving distance and low conductivity have been frequently encountered. A newself-diverting acid formulation was developed for use in stimulation jobs to try to solve the problems as described above. Evaluation of the viscosity, elasticity, rheological and gel-breaking performances of the self-diverting acids was performed through laboratory experiment. Communicating of fractures in the reservoir formations by acids was conducted through core flow experiment. The evaluation demonstrates that the self-diverting acid causes low damage to reservoir formations, the gels are easy to break, and the acid is evenly distributed. When the residue acid had its concentration decreased to 5%, the viscosity of the acid can be 96 mPa²s. The acid can go laterally to make the natural fractures communicated extensively, satisfying the needs to improve the marlstone reservoir. Comparison of the conductivities of the fractures using different improvement techniques resulted in a volumetric stimulation model suitable for marlstone reservoir improvement, a model integrating diverting acid fracturing and fracturing with sand. This technology has been used in the improvement of three wells (15 segments), obtaining stable daily production rate that is 10 times of the old wells.
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Key words:
- Marlstone /
- Self-diverting acid /
- Natural fracture /
- Network fractures /
- Conductivity
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