Alfred Davletbaev

Heavy Oil and Bitumen Recovery Using Radiofrequency Electromagnetic Irradiation and Electrical Heating: Theoretical Analysis and Field Scale Observations

Heavy-oil and bitumen recovery from difficult geological media such as deep, heterogeneous and high shale content sands and carbonates, and oilshale reservoirs requires techniques other than conventional thermal and miscible injection methods. Materials in oil reservoirs (formation water, crude oil, oil-water emulsions, bitumen and their components like resins, asphaltenes, and paraffin) are non-magnetic dielectric materials with low electrical conductivity. If the electromagnetic field can be created to change these properties, electro-thermo controlled hydrodynamics could improve the displacement and recovery of heavyoil/bitumen. This paper deals with the recovery improvement of heavy-oil/bitumen by Radio-Frequency (RF) Electromagnetic (EM) radiation. The RF-EM fields in the form of waves can penetrate deeply enough from fractions of a meter to several hundred meters into oil and gas containing reservoirs to generate heat and eventually improve recovery mainly due to the reduction of oil viscosity. The recovery mechanisms and the dynamics of the RF-EM heating process were analyzed for several field scale applications in Russia. In the Yultimirovskaya tar sand deposits, RF-EM energy was transmitted from the RF-EM generator, located at the surface, into the formation by a coaxial system of the well pipes. Another field example analyzed was the RF-EM stimulation process in several wells of the Mordovo-Karmalskaya tar sands performed in the 1980s. It was observed that the formation was heated to the temperature which was sufficient for injection of oxidant (air) to initiate fire flooding. Then, a mathematical model of this process was presented with a sample exercise. Some data needed for this exercise were obtained from the field tests evaluated. Field tests proved the efficiency of the RF-EM stimulation of heavy oil / bitumen deposits with low water cut values (in operating production wells with water cut <30% on early field development stages). Numerical simulations suggest that bottomhole temperature and heat/mass transfer effects in the reservoir can be controlled by setting the output performance of the RF generator and by the difference between the reservoir and bottom-hole pressure. Introduction Applying radio-frequency electromagnetic energy (RF-EM) into heavy-oil reservoirs is an unconventional stimulation method. The RF-EM radiation generates a volume source of heat in the reservoir rock. Due to dielectric absorption in the medium, the EM energy transforms into thermal energy, and the resulting heat reduces the viscosity of the reservoir fluids. Results of RF-EM treatment experiments were well documented in numerous studies (Chakma and Jha, 1992; Kasevich et al., 1994; Nigmatulin et al., 2001; Ovalles et al., 2002). Theoretical aspects of heavy-oil production were covered by Abernethy (1976), Islam et al. (1991), Sahni et al. (2000), Sayakhov et al. (2002), and Carrizales et al. (2008). Several other studies investigated the heat and mass transfer processes in heavy oil reservoirs stimulated by EM radiation (Sayakhov et al., 1998; Kovaleva and Khaydar, 2004; Kovaleva et al., 2004; Davletbaev et al., 2008 and 2009). A number of other investigations proposed analytical models of lab experiments (Hiebert et al., 1986; Ovalles et al., 2002).

Cold heavy oil production and production by radio-frequency electromagnetic radiation: Comparative numerical study

Comparative analysis for “cold” heavy oil production from fractured well in low-permeability formation, as well as heavy oil production by radio-frequency electromagnetic heating has been carried out. The results of mathematical modeling for both these technologies taking into account different fracture’s lengths show that the thermal method is most effective for more “short” fractures up to some their optimal size 5-10 m.

Fracture-Based Strategies for Carbonate Reservoir Development

Carbonate reservoirs present both opportunities and challenges, especially in rocks that contain multiple, heterogeneous porosities. This study addresses a large carbonate reservoir with complex porosity types including porous matrix, fractures, faults, and vuggy zones. A fracture-focused strategy considers how these porosities behave in oil production, and uses this understanding to improve reservoir productivity. The subject of this work is a major carbonate reservoir that was initially developed by conventional methods. These approaches emphasized matrix properties using petrophysically-interpreted wireline logs. The early stages of production, which did not include pressure maintenance, found anomalous behaviors that were inconsistent with a matrix-only reservoir. The existing petrophysical data, which are valid only for porous rock, could not address fracture-based hypotheses. A program of fracture studies supported a re-analysis of the production strategies in light of reservoir’s observed behaviors. The fracture-focused strategy employed FMI image logs along with production logs (PLT surveys) and temperature surveys. These well-based tools identified the locations of flow and their associated geologic features, which are appeared to be mainly fractured and vuggy horizons. Coring activities validated the FMI interpretations. A reexamination of well tests using supported a single-porosity, fracture flow model. Pressure derivative interpretations using fracture-based conceptual models associated well performance with geologic features, including both the vuggy zones and faults. The fracture-focused characterization program has developed improved conceptual models of the reservoir to support evolving production approaches including well acidizing, and other. The paper provides examples of successful well operations performed after appropriate field research.