低温高强韧性水泥浆在致密油水平井的应用

长庆油田致密油延长组油层埋藏浅，井底静止温度低，常规水泥石强度发展慢、脆性强，大型体积压裂易导致水泥环密封完整性破坏，严重威胁致密油开采和油井寿命。针对以上难题，优选了低温促凝早强剂DRA、低温增强材料DRB和膨胀增韧材料DRE-300S，并结合配套固井外加剂，开发了综合性能良好的低温高强韧性水泥浆体系。该水泥浆体系在55℃条件下，24h抗压强度达到35.8 MPa，168 h抗压强度为50.6 MPa，抗压强度较常规体系提高了33.1%，弹性模量降低了14.3%，表现出良好的低温高强韧性特性，增强了水泥环在交变应力作用下的密封完整性。该体系在长庆致密油水平井φ139.7mm生产套管固井中进行了4次现场应用，现场应用效果良好，为低温高强韧性水泥浆体系的推广应用奠定了技术基础。 

Cementing Tight Reservoir with Low Temperature High Strength Tough Cement Slurry

The Yanchang tight reservoir in the Changqing has shallow burial depth and low static bottom hole temperature. Conventional cement slurries used in this area produced highly brittle set cements with strengths that are developed very slowly. In large-scale stimulated reservoir volume fracturing, the brittle set cement easily lost its integrity, severely endangering the production of tight oil and the production life of the well. To solve these problems, a low temperature high strength tough cement slurry has been formulated with a low temperature accelerating early strength DRA, a low temperature strengthening material DRB, a low temperature toughness improving agent DRE-300S, and some other cement slurry additives. This cement slurry, at 55℃, had 24-hour compressive strength of 35.8 MPa, and 168-hour compressive strength of 50.6 MPa. Compared with conventional cement slurries, the compressive strength of this cement slurry was increased by 33.1%, and the elastic modulus reduced by 14.3%, showing good low temperature toughness. The sealing integrity of the cement sheath under the action of alternating stresses was greatly improved. This cement slurry has been successfully used four times in cementing the φ139.7 mm production casing string in horizontal wells in Changqing Oilfield, providing a technological base for the application of low temperature high toughness cement slurries.