Le'an Heavy Oil Reservoirs In Thermal / Chemical Handling Mining Technology

Le'an oilfield is a glutinite reservoir with utra-heavy oil and middle depth, it is produced by steamflooding. To overcome the steam override, steam channeling and poor oil recovery rate of hot water zone, thermal/chemical combined oil recovery technology was developed in 1980's. Although many works have been done, the study in this field is still at earlier stage. Nowadays the mechanism of this technology has not been well interpreted. There was not a perfected mathematic model to describe thermal/chemical combined oil recovery technology.In this paper, we have investigated the characteristics of thermal/chemical combined oil recovery technology based on experimental, theoretical and numerical studies. The mathematical model was developed and this model was solved using numerical method. The numerical simulation software of thermal/chemical combined oil recovery technology was programmed. The main points of this paper are as follows.(1) Impacts of surfactants were anlysised, it was included reducing adhension work and interfacial tension (IFT) as well as emulsifing. PS-I was chosen as a viscosity-reducing agent, XG-I as a displacement anget. The experiments including the tests of physical-chemical properties of surfactants under the condition of high temperature and thermal/chemical combined flooding performance were conducted. The results shown that surfactant types and its concentration, subsurface water properties, high temperature, and so on affected the role. The most incremental oil recoveries from steam flooding to thermal/chemical combined flooding could be reached to 19.65% .(2) The experiments of oil/water relative permeability of surfactants flooding were conducted for the high temperature and low- interfacial- tension system. The effects of temperature and interfacial tension on relative permeability were discussed and the mechanism was interpreted. An empirical model was developed to describe the oil/water relative permeability of high temperature-low tension system according to the experiment results. The model was in good agreement with relative permeability experimental data.(3) According to the mechanisms of surfactant adsorption, thermal degradation and chemical reaction of surfactants with mineral ions, a model of surfactant transport in porous media saturated by oil and water was presented. This model considered more factors reasonably than foreigner's model and could describe the real surfactant transport process in the core. The model was solved using finite difference method coupling with oil-water mass conservation equations and energy conservation equation. The effects of temperature, displacement velocity and slug size on surfactant transport process were discussed. Surfactantadsorption at the solid-liquid interface was modeled with Langmuir-type model and surface excess model, respectively. The surface excess model was firstly used to study surfactant adsorption under multiple-phase flow condition. (4) According to the mechanism of thermal/chemical combined oil recovery technology, three-dimensional, multiple-phase and multiple component model of this combined oil recovery technology was developed. Phase equilibrium and effects of temperature and interfacial tension on multiple-phase flow in porous media were considered in this model, so it is more perfect and more reasonable. The models were solved by fully implicit method and the surfactant transport equation was solved by implicit method. Model calculations indicate that the algorithm of the software is stable and the process is relative sample.(5) Histotric simulation for Well C37 was finished by steamflooding simulation software, it is difficult to injiection steam. Thermal/chemical cyclic injection and thermal/chemical flooding were simulated by 3D3P, multiple-component reservoir simulation software in order to anlysis the effects of injiection and work parameters on oil production, to optimize them. The data displays that thermal/chemical flooding can effectly reduce injection steam pressure and arise the oil production...