Study On Heavy Oil Reservoir Flow Mechanism And Selecting The Optimum Development Scheme

Mechanism of heavy crude oil flow in reservoir rock is significantly different from that of conventional crude oil because of high viscosity and complicated composition. Therefore, it is more difficult to effectively develop heavy crude oil reservoir than that of light oil reservoir. Studying heavy crude oil flow mechanism has an important role in guiding efficiently development of crude oil reservoir. In this paper,** well block of Wutonggou Group in Xinjiang oilfield, for example, systematically studied reservoir rock petrophysical properties, mechanism of heavy crude oil flow in reservoir and waterflood displacement under different conditions in order to provide some fundamental instructions to the development of heavy crude oil reservoirs.Through systematically experimentally and theoretically studied, the main findings in this paper can be summarized as follows:1. Reservoirs characteristics study indicated that the average permeability and porosity of P3Wt1 horizon which is the main horizon of** well block are 175.2mD and 21.8%, respectively. And the average permeability and porosity of P3Wt2 horizon are 59.9mD and 21.2%, respectively. Consequently, the reservoir of ** well block has good flow capacity.2. Viscosity-temperature and rheological experiments demonstrated that heavy crude oil flow in reservoir rock of** well block still comply with the classical Darcy’s law. Flow velocity of heavy crude oil in reservoir rock is linearly proportional to the driving pressure gradient under formation temperature and pressure conditions.3. It was found that the irreducible water saturation of** well block is relatively high and the simultaneous flow region of water and oil is very small. Additionally, water relative permeability at residual oil state is also very small. Theoretical computer showed that the waterflood ultimate recovery efficiency ranged from 10.2% to 18.2% and its average value is 14.5%.4. The average oil displacement efficiency displaced by hot water is about 42% which is almost the same with that firstly displaced by cold water then by hot water. However, the average oil displacement efficiency displaced by cold water is only about 23%.5. Different oil displacement experiments indicated that carbon dioxide immiscible oil displacement efficiency is higher than that displaced by hot and cold water. The average oil displacement efficiency firstly displaced by cold water then by carbon dioxide is about 47%.6. The producing level of** is low when the reservoir adopts commingling production and the average oil displacement efficiency is only 16%. Vertical and fractured well productivity equations considered reservoir rock permeability stress-sensitivity and water sensitivity were also derived in this paper. Theoretical calculations showed that the fractured well productivity is the twice as that of vertical well under the same driving pressure. The reasonable well spacing of Ji 006 fault block is about 210m and the reasonable well productivity is 6t/d. Furthermore, the reasonable well spacing and well productivity of other fault block of** well block are 180m and 5t/d, respectively.