稠油蒸汽吞吐辅助层内水热催化裂解数值模拟研究

Numerical Simulation of Steam Huff-and-Puff Assisted Catalytic Aquathermolysis on Heavy Oil

稠油蒸汽吞吐辅助层内催化裂解过程中,层内原油随温度场分布不同而发生不同程度的化学改质,为近似模拟层内原油的这一变化,预测稠油蒸汽吞吐辅助层内催化裂解后油井的产能,在蒸汽吞吐数值模型及催化裂解作用机理的基础上,仅考虑油、水两相流动,不考虑重力和毛管力作用,将地层中的温度场分布对稠油催化裂解的影响,表征为不同温度范围内地下稠油黏温曲线的变化,并将该变化引入成熟蒸汽吞吐数值模拟模型,建立了二维两相蒸汽吞吐辅助催化裂解数值模型,并给出了求解方法。利用所建模型对孤东K92N6井第3轮次蒸汽吞吐辅助催化裂解矿场试验进行了模拟计算,该井该轮次预测周期产油量为4 560.4t,实际产油量为4 899.7t,预测误差为6.92%,预测精度符合工程要求。研究结果表明:根据蒸汽吞吐过程中井周温度分布,将催化裂解原油分为未反应型、低温反应型和高温反应型,并将这3类裂解改质后稠油的黏温关系回归成温度的指数函数,引入到成熟蒸汽吞吐模型,可实现层内稠油蒸汽吞吐辅助催化裂解不可逆改质过程的数学近似表征模拟,模拟结果可以为蒸汽吞吐辅助层内催化裂解技术工艺参数的优化、产能预测提供依据。

During heavy oil catalytic aquathermolysis assisted by steam huff and puff,chemical properties of crude oil within these formations may vary to some degree due to temperature distribution differences.To appropriately simulate such changes of crude oil in these formations and predict well productivity with steam-assisted huff-and-puff in heavy oil development,the impact of distribution of temperature fields within the formation on heavy oil catalytic aquathermolysis are expressed in terms of viscosity change versus temperature.In the simulation,only the two-phase flow of oil and water are considered while gravity and capillary forces are not taken into account.Then those changes are introduced into the well-developed model in numerical simulation of steam-assisted huff-and-puff operations to construct numerical model for2Dtwo-phase steam-assisted huff-and-puff operations.In addition,techniques available to obtain relevant solutions are also provided.The model was used to simulate field tests of the fourth round of steam-assisted huff-and-puff catalytic aquathermolysis in Well K92N6 in the Gudong Oilfield.According to calculation results,oil production in this round of development would be around 4 560.4t,while the actual production during the period was determined to be 4 899.7t.The difference between actual and simulated was reasonable,about 6.92%,which could meet engineering requirements.Research results demonstrated that crude oil for catalytic cracking can be classified into three categories：unreacted,low-temperature reactive and high-temperature reactive according to temperature distribution around the borehole during steam-assisted huff-and-puff.The viscosity-temperature relationships of crude oil after cracking and modification of the three types can be placedinto theexponential function of temperatures and then be introduced into a mature steam-assisted huff-and-puff model to perform mathematically approximate characterization and simulation of the irreversible property changing progress in catalytic cracking during steam-assisted huff-andpuff processes.Relevant simulation results will provide guidance in optimization of technical parameters and inthe prediction of productivity for catalytic cracking techniques in steam-assisted huff-and-puff operations.