高温热储环境下微气泡钻井液特性及作用机理研究

In the energy transformation and beautiful home construction environment, geothermal energy is becoming more significant. Drilling is the only way to develop geothermal energy buried underground, which accounts for about 1/3- 1/2 of the total cost of the electricity.On one hand, drilling fluid loss causes many drilling/completion problem and increases cost; On the other hand drilling cuttings intrudes into geothermal reservoir which resulting in the decrease of productivity. Drilling with Colloid Gas Aphron (CGA) can achieve nearly balance to prevent leakage, and CGA can realize temporary sealing to protect the permeability of the reservoir. CGA driling can achieved with the conventional drilling fluid mixing equipment and mud pump, saving the expensive cost for aerated drilling, reducing the cost of geothermal well drilling. However, the temperature of geothermal drilling is higher, the fissures are more developed, thermal reservoir lithology and the geothermal fluid is more complex, which will have a great influence on the physical and chemical properties of CGA and CGA drilling fluid. This project intends to research the following aspects under high-temperature thermal reservoir environment: 1) CGA physicochemical characteristics and drilling fluid properties of CGA and the influencing factors; 2) CGA drilling fluid rheology and filtration performance and the impact factors; 3) the CGA drilling fluid plugging characteristics and mechanism of action; 4) formation protection of CGA drilling fluid and its mechanism.

在能源转型以及美丽家园建设的环境下，地热能受到进一步重视。钻井是勘探及开发地热能的唯一途径，其成本占地热发电总成本的1/3-1/2，甚至更高。钻井液漏失一方面引发诸多钻/完井问题，增加成本；另一方面钻屑漏失侵入热储，会导致产能降低。微气泡（Colloid Gas Aphron-CGA）钻井液可实现近平衡钻井预防漏失，同时CGA对热储可实现暂堵，保护其渗透率。而且，CGA钻井液可以利用常规设备进行搅拌配制和泥浆泵循环，节省了充气钻井昂贵的高压设备费用，对降低地热钻井成本具有重要意义。然而，地热钻井热储温度更高、裂隙更加发育、热储岩性和地热流体更加复杂，这对CGA的物理化学和CGA钻井液的特性影响重大。本项目拟研究高温热储环境下，1）CGA和CGA钻井液的物化特性及其影响因素；2）CGA钻井液的流变和滤失等性能及影响因素；3）CGA钻井液堵漏特性及作用机理；4）CGA钻井液保护热储及作用机理。

微泡钻井液（Colloid  Gas Aphron-CGA）可实现近平衡钻井预防漏失，同时CGA对热储可实现暂堵，保护其渗透率，对降低地热钻井成本具有重要意义。然而，地热钻井热储温度更高、裂隙更 加发育、热储岩性和地热流体更加复杂，这对CGA的理化特性影响重大。本项目结合文献调研与前期实验，发现发泡剂的热降解和稳泡剂的高温降粘作用显著降低了CGA的抗高温性和高温稳定性，这是制约CGA钻井液在高温地热井中应用的关键因素，进而提出了研制“高温稳定、抗盐抗钙、环保性好”新型钻井液处理剂的可行方向。此后，本项目研制出环保型抗高温（240℃）、抗盐抗钙（36%NaCl、不低于10%CaCl2）钻井液处理剂，包括稳泡剂兼降滤失剂EST、起泡剂AGS-8和AGS-12、润滑剂ChCl-PEG，评价了Nano-SiO2的协同效应，构建出满足高温干热岩型地热钻井（CGA-1）和高温高矿化度水热型地热钻井（CGA-2）需求的环保型微泡钻井液体系。针对“表面活性剂/聚合物”体系和“表面活性剂/聚合物/纳米颗粒”体系，深入地开展了稳泡机理研究，提出了“吸附、增粘、交联”综合稳泡效应。探讨了CGA保护储层的原理，初步提出了“颗粒封堵机制”。本项目研究突破了微泡钻井液在超高温钻井中的应用局限，解决了其在高温环境下抗盐、抗钙性不足的问题，丰富了高温地热钻井技术，助力于地热资源的经济化勘探开发。