Research And Case Study On The AMR Software Development For Thermal Recovery Of Heavy Oil By Steam Injection

The numerical reservoir simulation has become an important tool for the petroleum research and exploration. The thermal recovery by steam injection can be thought as the problem of multi-phase flow in porous media with the phase-change. In the processes, there are sharp moving interfaces of temperature and phase saturations in the reservoir. Due to the rapid variations of the physical quantities across the interface, very fine grids are required. As a result, a huge CPU time and memory are needed if applying a uniform grid to the whole calculation area. In this paper, the adaptive mesh refinement (AMR) technique is applied to the numerical simulations for the processes of thermal recovery by steam injection, where the different heterogeneous cases of the reservoir are considered, like the reservoir with the permeability variations, the different rock-types, the heterogeneous fractured porous media, the complex boundary or complex faulted reservoir. In the AMR technique, the front is tracked, in order to have fine grid blocks in the region with steep gradients but coarser grid blocks ahead and behind of the front. The proposed AMR technique is fast and can give good accuracy. On the basis of theoretical research, a software package for the reservoir simulations, where including the AMR technique, is developed. This software package has good precision and numerical stability to meet the demands of scientific research.With the use of the software developed by ourselves, a numerical example of SAGD progress in fractured reservoirs and a numerical simulation of the hot water flooding process of block Shan2are carried out, whose results are compared with the one based on CMG-STARS, a well-known commercial reservoir simulation software. The comparison shows that the computing speed of our software is five times of the one of CMG-STARS. The calculated results of day steam injection, day oil production, cumulative water injection and cumulative oil production are in good agreement with those of CMG-STARS. The remaining oil saturation distribution within the reservoir is relatively consistent with the one of CMG-STARS.Using our own developed software, we perform a numerical study of Steam and Gas Push (SAGP) and Expanding-Solvent Steam-Assisted Gravity Drainage (ES-SAGD), which are both improvements of SAGD. In the gravity drainage process, the key to heavy oil production is the mobility of the oil phase which is dominated by the viscosity of the oil phase. The objective of this numerical study was to investigate the drainage mechanism of co-injecting light and heavy solvents to improve production performance. The light solvent C2H6, delivered in the vapor phase to the entire fluid interface, keeps the pressure of the steam chamber, and reduces the thermosteresis by building a thick gas blanket on the top of the recovery, but the recovery ratio may become lower due to the lower temperature of the steam chamber. The heavy solvent C9H20owould condense, with condensed steam, at the boundary of the steam chamber. Condensed solvent around the interface of the steam chamber which dilutes the oil, in conjunction with heat, reduces its viscosity and increases its mobility thereby increasing the oil production rate and recovery ratio. The conclusions from this study can be used to design suitable solvent mixtures and co-injection strategies to deliver a higher production rate and recovery ratio.Heavy, high water and low permeability formations crude oil show a characteristic of non-Newtonian fluids. Many non-Newton fluids such as polymer solution, micellar solutions, emulsions and foam concentrate of high compression coefficient are used as oil displacing agents in the EOR process. Usually, the drilling fluid and the fracturing fluid in the hydraulic fracturing technology are usually non-Newtonian fluids. Therefore, the study of transport of non-Newtonian fluids in porous media has important practical significance for oil and gas development.As a common non-Newtonian fluid, the constitutive equation of power-law fluids is relatively simple and can better reflect the rheological properties of heavy oil. The large-scale continuum models for transport of power-law fluids in porous media is derived from the pore-scale control equations using the volume averaging method. The averaging procedure leads to an equation of motion and a continuity equation expressed in terms of the volume-averaged pressure and velocity. The closure problem for the power-law fluid flow is assumed to be analogous as the Newtonian fluid flow. Then a tensorial form of Darcy-scale filtration equation is obtained and the power-law relation between the averaged velocity and the gradient of the averaged pressure are confirmed. Different from Newtonian fluids, the apparent permeability significantly depends upon the filtration velocity direction for higher dimensional flow (d≥2). Numerical test also validates this conclusion.In summary, the object of this paper is to develop an AMR software package for numerical reservoir simulation in thermal recovery of heavy oil by steam injection, based upon the research of the AMR technique for the thermal recovery of heavy oil in complex stratum. With the use of our own developed software, we studied different light solvent extraction efficiency of SAGD process and mechanism. For non-Newtonian behavior of heavy oil, the volume-average method was used to study the transport of power-law fluids flow in porous media and derive its generalized Darcy’s law.