Yegane, Mohsen Mirzaie (Sharif University of Technology) | Bashtani, Farzad (PERM Inc) | Tahmasebi, Ali (Digital Core Analysis Laboratory, University of Calgary) | Ayatollahi, Shahab (Petroleum University of Technology) | Al-wahaibi, Yahya Mansoor (Sharif University Of Technology)
The application of the renewable energy sources, especially solar energy, for thermal enhanced oil recovery methods as an economical and environmental valuable technique has received many attractions recently. Concentrated Solar Power systems are capable of producing substantial quantities of steam by means of focused sunlight as the heat source for steam generation. This paper aims to investigate viability of using this innovative technology in fractured reservoirs to generate steam instead of using conventional steam generators.
A synthetic fractured reservoir with properties similar to those of giant carbonate oil reserves in the Middle East was designed by using commercial thermal simulator. The dual porosity model was used to account for differences in matrix and fracture parameters. Different cyclic and continuous steam injection scenarios using combination of both solar energy and fossil-fuel to generate steam were designed. The cyclic scenarios were different in terms of contribution of solar energy in steam generation and in case of 100% solar scenario a small nightly steam injection using fossil-fuel was suggested to prevent flow back into the wellbore.
It was assumed that total amount of injected steam in 10 year time period is the same for all the scenarios regardless of how steam was generated. Simulation results showed that nightly injection of insignificant amount of fossil-fuel-generated-steam in a 100% solar-generated-steam injection process increases the cumulative oil production compared to 100% solar-generated-steam injection system with no nightly injection. Furthermore, there was no significant difference between the final oil recoveries for all the designed cyclic injection scenarios. Although continuous steam injection scenario had the highest final oil recovery among all scenarios, a detailed economical study showed that net present value for 100% solar-generated-steam scenario is the highest. An environmental analysis on all scenarios also indicated significant reduction of CO2 emission into the atmosphere for the latter scenario.
Therefore, hybrid steam generators which utilize solar energy instead of traditional fossil-fuel for steam generation is proposed for Middle East fractured reservoirs where there is abundance of sunshine during day time. The findings illustrate high economic efficiency of solar-generated steam injection and highlight it as a green EOR method.
Habibi, Ali (U. of Tehran) | Al-Hadrami, Hamoud Khalfan H. (Sultan Qaboos University) | Al-ajmi, Adel M. (Sultan Qaboos U.) | Al-wahaibi, Yahya Mansoor (Sultan Qaboos University) | Ayatollahi, Shahabbodin (Shiraz University)
Fines migration is the major reason for productivity decline known as formation damage in oil reservoirs. Sandstone formations are sensitive to brine salinity alteration which disturbs equilibrium condition in porous media. Because of nonequilibrium condition fines migration occurs during various operations. Nanoparticles seem to be good candidates to strengthen the attractive forces between fines and pore wall due to very small size, high specific surface area and electrical surface charge.
In this experimental study, several tests were performed using Berea sandstone (8 wt% clays) cores (3 in. length and 1.5 in. diameter). MgO nanoparticles were stabilized in the water uniformly using surface active agent and ultrasonication. Total dimensionless energy of interaction between nano particles in the suspensions was calculated based on the DLVO theory. Various core flooding tests were conducted to determine the effect of MgO nanofluid injection as clay stabilizer at different brine salinities on the cores with the permeability from 600-100 md. The pressure drop across the core was measured.
The results indicated that the MgO nanofluid could fix fines effectively where brine salinity became lower than CSC. Besides, measured zeta potential and total energy of interaction calculation confirmed that repulsive force became dominant at the specific concentration of the complex nanofluid which ensures its stability for long time during core flooding tests.
Thus, MgO nanofluid significantly prevented water shock problem. Also, no significant reduction in permeability was noticed in any of core flood tests.
Fines are loose silica based particles present in the sandstone formation, which can detach and move easily as a result of ionic strength reduction or pH increase of injected fluid. Migratory fine particles can trap at throat levels which lead to permeability reduction of formation. Colloidal and hydrodynamic forces are found to be responsible for the fines detachment and their release from the pore surfaces. London Van der Waals attraction, double layer forces are the most dominant forces in the detachment of fines from porous media based on the DLVO theory (Khilar and Fogler, 1998; Schramm, et al, 1996; Ahmadi et al, 2011). Hibbeler et al, (2003) provide an excellent review on the practical recipes to reduce fines migration.
In this study, gas-oil gravity drainage process and steam-gas assisted gravity drainage processes for heavy oil recovery from fractured models were investigated experimentally. For each test, six oil- wet saturated outcrop cores, 8.7 cm in diameter and 15 cm length, were stacked in a long core holder. In the first step, gas injection was started into the model at reservoir condition that results in oil production under gas-oil gravity drainage mechanism. In the second round of tests when no more oil was produced by gas injection, the tests were continued using steam-gas assisted gravity drainage process. In this stage, gas was injected together with specific steam/gas ratio at saturated temperature condition. In the course of experiments, oil and water productions, pressure and temperatures of system were monitored carefully. The experiments were performed using three different combination of gases consist of pure CO2, pure N2 and mixture of 15 % CO2 and 85% N2 as synthetic flue gas. The results showed that after gas breakthrough and fracture depletion, the ultimate oil recovery for CO2 injection was 58.4 % (14.8% for gas injection and 43.6 % for steam-gas co-injection), in the case of flue gas injection, it was 73.8 % (9.8 % for gas injection and 64% for steam-gas co-injection) and for N2 injection was 47% (13.5 % for gas injection and 33.5% for steam-gas co-injection). The results indicate the high performance of flue gas injection for heavy oil recovery from fractured reservoirs during gas-oil gravity drainage and steam-gas assisted gravity drainage processes.
Al-Hattali, Rayah Rashid (Sultan Qaboos University) | Al-sulaimani, Hanaa Salim (Sultan Qaboos University) | Al-wahaibi, Yahya Mansoor (Sultan Qaboos University) | Al-Bahry, Saif (Sultan Qaboos University) | Elshafie, Abdulkadir (SUltan Qaboos University) | Al-Bemani, Ali Soud (Sultan Qaboos University) | Joshi, Sanket
Selective plugging by microbial biomass is one of the proposed mechanisms for improving reservoir sweep efficiency in fractured reservoirs. In this study, the potential of Bacillus licheniformis strains isolated from oil contaminated soil from the Sultanate of Oman was tested for their ability to grow in induced fractures in carbonate rocks and to divert subsequent injection water to the unswept matrix zones.
Three Bacillus licheniformis strains were tested with name codes; B29, B17 and W16. Their growth behavior using different nitrogen sources; yeast extract, peptone and urea was investigated. Glucose and sucrose were tested as carbon sources. Carbon/nitrogen ratios were optimized where it was found that sucrose was the carbon source that maximized bacterial growth at 2% concentration and yeast extract was the selected nitrogen source with concentration of 0.1%. The combination of B. licheniformis strain W16 in a minimal medium containing sucrose was the optimum condition for maximum cell growth within 10-12 hours of incubation. Standard Indiana limestone core plugs were used for coreflooding experiments where a fracture was simulated by slicing the cores vertically into two sections using a thin blade. The bacterial cells were injected into the cores and the ability of the microbes to grow and plug the fracture was examined. Scanning electron microscopy was used to prove the growth of the microbial cells in the fracture after the experiment.
Coreflooding experiments showed promising results where enhancement of oil recovery was observed after bacterial injection. A total of 27-30% of the residual oil was produced after 11 hours of incubation. This shows the high potential of using microbial biomass for selective plugging in fractured reservoirs.
This paper reports the results of extensive experimental and numerical studies of the effects of well-defined heterogeneous oil-wet porous media (lenses) on simultaneous first contact miscible water alternating gas (FCMWAG) displacements. Flow displacement and effluent profiles have been obtained from well-characterized laboratory experiments in two-dimensional heterogeneous beadpacks. The effects of WAG ratios have been examined. All experiments were then modeled using IMPES finite difference simulator without using history matching (all simulations used directly measured porous media properties as inputs) to quantify the accuracy of the simulation when modeling the FCMWAG displacements in a porous media with lenses heterogeneity. Results revealed that neglecting lenses heterogeneity will cause incorrect reservoir engineering interpretation; for example that of core floods for absolute permeability, relative permeability and residual oil saturation determinations.