基于氮气诱导的深水井喷插入式隔水管应急收油优化

Optimization of the riser insertion tube based on the nitrogen induction for the deepwater blowout emergency response

以插入式隔水管应急技术为研究对象,依据现场工艺及Beggs-Brill计算模型,构建其工艺流程分析模型。通过与深水地平线事故数据对比,该模型预测油气回收量平均误差为5.85%,可较为准确地描述现场情况。考虑注入抑制剂甲醇降低水合物形成风险,从提高收油效率角度开展氮气对油气回收诱导作用的研究,进而提出油气回收量单位改变率指标,以优化氮气注入量。鉴于该技术存在密封失效风险,探究回收油气含水量对氮气最优注入量及最大油气回收量的影响。结果表明:在收油管道出口压力一定、注入甲醇抑制水合物形成的情况下,注入氮气能够显著提高收油效率,以深水地平线事故为例,最大可使油气回收量增大18%;从预防水合物形成和便于现场作业的角度,推荐以油气回收量最大时的甲醇注入量为插入式隔水管作业时的甲醇用量;回收油气含水量增大时,氮气最优注入量以近似线性趋势增大,最大油气回收量则线性减小。

This paper is aimed to enhance the efficiency of the riser insertion tube, which is one of the quick-response techniques 1o be applied for the deepwater environment accidents. Based on the multi- phase flowing method and the Beggs-Brill related math model, we have established a process-analyzing model of the riser insertion tube tool. And, then we have validated the multiphase flow model by making a comparison and contrast against the field data gained from a deepwater environment accident, confirming that the mean deviation of the model from the catual accident tends to be 5.85 %. The afore- mentioned result also implies that the model is suitable for describing the field process to a reasonable extent. Hence, the validated model has enabled us to take up ihe project for strengthening the hydrocar- bon recovery via nitrogen. What is more, even when the outlet pres- sure of the recovery pipe remained unchanged, it would still be possi-ble for the amount of injected nitrogen to rise up gradually. Besides, as we can see under the deep water environment, even if the pressure can be very high whereas the temperature there is rather low, methanol can still be injected to inhibit the hydrate formation. The proposed model has also accounted for the volume of nitrogen that should be injected to enhance the hydrocarbon recovery effectively, which should be 18% for the Deepwater environment accidents, to the maximum growth. So far as the hydrate inhibition is concerned, we have established the methanol injection flow rate as the maximum hydrocarbon recovery rate so as to leave for a safety margin. And, fi- nally, it would be possible to level off the hydrocarbon recovery flow rate with the increase of the injected nitrogen. It is just for the above said reasons that we have put forward the rate for exchange of the hy- drocarbon recovery to optimize the nitrogen injection rate. Given that the system were not completely sealed up, the water content of the recovered hydrocarbon could still be made to rise up enough. There- fore, the optimal nitrogen rate and the maximum hydrocarbon recov- ery flow rate we have developed should be taken as our main research patent on the effects of the water content. To be exact, the findings should be stated as formally： with the increase of the water content, the optimal nitrogen injection flow rate tends to go up following an ap- proximate linear trend while the maximum hydrocarbon recovery flow rate tends to decrease in the same manner.