||Controlling the hybrid steam-solvent injection for increasing recovery factor and reducing solvent retention in heterogeneous reservoirs
||The irregular steam chamber propagation has been a problem in hybrid steam-solvent injection in heterogeneous reservoirs. When the steam chamber is poor, the solvent passes through to the production well directly. If the steam chamber is good, the oil drain will be effective. In such a case, controlling the hybrid steam-solvent injection is necessary to spread the steam chamber uniformly. A synthetic reservoir model was developed to study the phenomenon using a real field data set. Adjusting steam injection pressure, grouping perforations, and controlling the openings of perforation were observed. The adjustment from the peak of production rate is more favourable
because the steam chamber has reached its maturity. Then, the solvent effectiveness increases and the solvent retention reduces. The heat efficiency and recovery factor are increased by 7.4% and 8%, respectively. The NPV on the adjustment from the peak of production rate increases by 9% compared with no-adjustment case.
||Smart completion design in cyclic steam stimulation process: an alternative for accelerating heavy oil recovery
||Cyclic steam stimulation (CSS) has succeeded in recovering bitumen and heavy oil. However, after the fifth cycle, the process is no longer effective as indicated by the increasing cumulative steam-oil ratio (cSOR). This paper proposes an improvement to the CSS performance by modifying the completion design. The perforation interval is divided into two parts: upper section (for injection) and lower section (for production). In such design, the injected steam would condense due to heat loss. The steam would then flow to the lower section because of gravity force and the oil starts to produce. The injection-production cycle is managed by an interval control valve (ICV).
Simulation results show that the proposed design would reduce the cSOR up to 30% and increase the cumulative oil production by 3.5 times. It is also revealed that the longer the distance between the injection and production sections, the better the steam efficiency.
||An Investigation of Hybrid Steam-Solvent Injection for Increasing Economy and Reducing CO2 Emission
||The hybrid steam-solvent injection scheme has been applied but limited results have been reported in the literature. The optimum solvent concentration to maximize economics and to reduce the CO2 emission is still in question. A synthetic reservoir model was developed using real field data to study such an injection. Results indicate that the optimal solvent concentration is 5.0% by volume fraction and as the concentration increases the CO2 emission reduces. The optimum case has 21% gain in the net present value discounted by 12% per annual and 9.1% reduction in the CO2 emission comparing to the pure steam injection.
||A Comprehensive Investigation of WASP Application in Heavy Oil Using Response Surface Methodology
||Steamflood has been performed successfully since the 1950’s in several fields worldwide. Although being considered successful, it still has problems associated with its mechanism. Due to gravitational effects, steam tends to move towards the upper portion of the reservoir causing the lower section to be poorly drained. In order to overcome this effect, water alternating steam process (WASP) might be a good solution which helps inhibiting the steam from moving upwards while keeping breakthrough-time from increasing. Previous literature study about WASP is scarce, even though this process is complex and sensitive to operating condition. By investigating WASP using response surface methodology, factors governing the steamflooding operations can be evaluated.
This paper presents the investigation regarding WASP applications in heavy oil. The reservoir model is ran with several operating conditions to achieve the most realistic interpretation. The operating variables include WASP start, WASP cycle, steam and hot water injection rate, and steam quality. Afterwards, a statistical model is fitted to examine the most important parameters influencing the 8-year net present value (NPV).
Simulation results indicate that the injection rate and WASP cycle are very sensitive to the NPV. The optimum case is that in which the WASP is started after 3.57 years, the cycle of steam-hot water injection is 4.65 months, the steam quality is 0.58, and the steam and hot water rate are 108 m3/day. The maximum NPV is 29.80 MMUSD.
||Smart Completion Design for Managing Steam Injection in CSS Process
||In conventional cyclic steam stimulation (CSS), steam is periodically injected at high pressure to the reservoir. After the steam injection period, the well is soaked for several days then it will be produced. Generally, for the first to the fifth cycle, the steam can effectively transfer the heat to the reservoir. After that, the CSOR will rise up indicating that the process is currently ineffective.
This paper aims to improve the CSS performance using modified well completion. The perforation is modified to become two parts, one part is on the top side (as injection) and the other part is on the bottom side (as production). In this process, after being injected, the steam will condense, resulting from heat loss, and it will move to lower part because of gravity drainage. Simultaneously, crude oil was produced through the production perforation. The opening-closing of the injection-production cycle is managed by interval control valve (ICV). To provide an overview of this phenomenon, a synthetic reservoir model was built based on Pertama-kedua formation, located in Sumatra Indonesia. Sensitive variables are length of the injection-production perforation and soaking time. Finally, the heat efficiency was evaluated during 8 years of project life.
Simulation results show that dividing the perforation into injection and production intervals will reduce CSOR 30% and this requires shorter soaking time compared to that of conventional processes. Furthermore, if the distance between injection and production interval is longer the production will be better. However, this gap is limited by reservoir thickness.
||Managing of Hybrid Steam-solvent injection distribution for Maximizing Recovery Factor in heterogeneous Reservoir
||Steam Assisted Gravity Drainage process has been done and successfully implemented for the producing of the Canadian heavy oils and bitumen. Although it is commercially proven, but it still uses high energy intensity and has high environmental impact. To reduce those side effects, hybrid steam-solvent is proposed as one of the alternative processes in order to reduce the problems. There are some challenges in reservoir heterogeneity correlated with steam solvent injection. In conventional process, spreading of steam-solvent is able to be controlled using bottom-hole pressure injection and liquid production rate. In heterogeneous reservoirs however, each part of the horizontal well will have different optimum operation conditions. This paper presents a strategy for hybrid steam solvent optimization using ICVs (interval control valves) to maximize energy efficiency. To provide an overview of this phenomenon, the synthetic reservoir model is built from McMurray Formation. Bitumen saturation distribution and rock properties are created using geostatistic method and validated using several wells. The reservoir models were run using several operating conditions to achieve the most realistic interpretation. Sensitive variables are steam injection pressure, length grouping of perforations, managing of perforation openings, and solvent concentration. Afterwards, steam efficiency and solvent affectivities are evaluated during 15 years of project life. Simulation results show that the managing of steam injection will increase heat efficiency up to 7.4% compared with conventional perforations. Furthermore, in the hybrid steam-solvent injection, the recovery factor will be better 8% compared to without adjustment in solvent concentration of 10% volume. Finally, retention of solvent injection can also reduce until 30% by this managing of processes.