Showing papers by "Pavel Bedrikovetsky published in 2013"

Mathematical Model for Fines-Migration-Assisted Waterflooding With Induced Formation Damage

Abstract: Permeability decline during corefloods with varying water composition, especially with low-salinity water, has been widely reported in the literature. This effect can provide a relatively simple method for mobility control during waterflooding. In this work, new basic equations for waterflooding with salinity variations causing the detachment of fine particles, their migration, and their straining are derived. The maximum concentration of attached fine particles as a function of water salinity and saturation is used to model the fines detachment. In large-scale approximation, the equivalence between the model for two-phase flow with fines migration and the adsorption-free polymer-flood model is established, which allows applying a commercial polymer flood simulator for modeling the waterflood with induced fines migration. The modeling showed that the permeability decline in the water-swept zone, caused by the alteration of the injected water composition and induced fines migration, may be able to improve waterflood performance by delaying water breakthrough, increasing sweep efficiency, and reducing the water cut, thus providing a relatively simple method for mobility control during waterflooding.

Size-exclusion colloidal transport in porous media - stochastic modeling and experimental study

Abstract: Suspension, colloidal, and emulsion flow in rocks with particle size-exclusion may have a strong effect on the reservoir and on the well behavior during fines migration and production, drilling-fluid invasion into oil- or gas-bearing formations, or injection of seawater or produced water. The stochastic microscale equations for size-exclusion colloidal transport in porous media (PM) are derived. The proposed model includes the following new features: It accounts for the accessible flux in the expression for capture rate, it accounts for the increase of inlet concentration caused by the injected particles entering only the accessible area, and it accounts for the dilution of effluent accessible flux in the overall flux of the produced suspension.

Exact Solution for Long-Term Size Exclusion Suspension-Colloidal Transport in Porous Media

Abstract: Long-term deep bed filtration in porous media with size exclusion particle capture mechanism is studied. For monodispersed suspension and transport in porous media with distributed pore sizes, the microstochastic model allows for upscaling and the exact solution is derived for the obtained macroscale equation system. Results show that transient pore size distribution and nonlinear relation between the filtration coefficient and captured particle concentration during suspension filtration and retention are the main features of long-term deep bed filtration, which generalises the classical deep bed filtration model and its latter modifications. Furthermore, the exact solution demonstrates earlier breakthrough and lower breakthrough concentration for larger particles. Among all the pores with different sizes, the ones with intermediate sizes (between the minimum pore size and the particle size) vanish first. Total concentration of all the pores smaller than the particles turns to zero asymptotically when time tends to infinity, which corresponds to complete plugging of smaller pores.

Fines Migration in Fractured Wells:Integrating Modeling, Field and Laboratory Data

Abstract: Production and drawdown data from ten subsea deepwater fractured wells have been modeled using an analytical model for unsteady state flow with fines migration. The simulation results and the field data indicated a good match within five percent. A sensitivity study conducted on initial concentration of fines, flow rate, maximum fines mobilization velocity, fines distribution, formation damage and filtration coefficients confirmed that the model matching parameters are within values commonly reported in the literature. This paper describes the methodology used to integrate the modeling predictions with field and laboratory data to identify probable causes for increasing skins and declining productivity index (PI) values observed in some of the wells under investigation. The good match between the modeling and the field data, further validated with laboratory experiments, allows for discussion of long term predictions on well productivity impacting current reservoir management strategies and field development plans.

A Novel Water Injectivity Model and Experimental Validation using CT Scanned Core-Floods

Abstract: Injectivity decline is an issue during produced-water reinjection (PWRI) for water disposal in aquifers, waterflooding, chemical enhanced oil recovery, and geothermal-energy exploitation. A novel model for injectivity decline under flow conditions reminiscent of PWRI was developed taking into account deep-bed filtration and buildup of external filter cake. A distinct feature of the model is that it describes particle-retention kinetics responsible for internal filtration by an exponential decaying function of the retained-particle concentration. The corresponding nonlinear governing partial-differential equations were solved numerically and coupled with a known analytical model for external filtration with the concept of transition time. Coreflood experiments consisting of the injection of brine containing suspended hematite particles (volume fractions in the range of 2 to 6 ppm) were also performed. Computed-tomography (CT) scans of the core were taken to obtain deposition profiles along the core at different times. In addition, effect of various parameters (particle concentration and number of grids) on injectivity was investigated. From CT-scan and optical-microscope analyses, it was found that surface deposition in the porous medium and face plugging at the injection face of the core were responsible for decline in injectivity. The transition time from pure internal to external filtration was accurately determined from the CT-scan and pressure data. The newly proposed model and experiments were found to be in excellent agreement, indicating that the adopted retention function is a good heuristic description of particle retention.

Productivity decline due to fines migration (modelling and field case study)

Abstract: High formation damage, including that induced by fines migration has been reported in numerous geothermal projects. The attaching electrostatic forces acting on fines are weak at high temperatures if compared with drag and lifting forces, which detach the particles from grain surfaces. Migration of lifted fines results in their straining in thin pores preferentially near to well, causing severe permeability and productivity decline. A mathematical model has been developed, based on recently developed theory of particle detachment in suspension flows. Solution for predicting well productivity is obtained. The model is validated by comparison with the field data from geothermal well A in Australia. Productivity decline due to fines migration is more likely to happen in high temperature geothermal reservoirs if compared with conventional aquifers or oil and gas fields.

Determining Rate Profile in Gas Wells from Pressure and Temperature Depth Distributions

Abstract: Gas flow profile along the wellbore is an important piece of information for reservoir and production management purposes, since it provides flow contribution from each producing interval along the wellbore, which is critical for optimizing well performance and maximizing recovery of reserves. Traditional methods are expensive, particularly in high temperature wells and involve running production logsging tools (PLT's) along with flowmeters. Deployment of production logging tools into a well can be operationally difficult and typically requires flow to be suspended temporarily to allow the tools to be run in hole. This can have a negative impact on the quality of data collected, potentially making it un-representative of normal producing conditions. A simple and effective method of the gas rate prediction from temperature and pressure data is discussed in this paper. Solving the inverse problem allows determination of the flow rate and thermal conductivity of the formation by matching the gas pressure and temperature distributions with measured profiles. The results of field data treatment show good agreement with the model prediction and are consistent with flowmeter (PLT) data. Besides, the approximate estimate from direct averaging using the measured data shows good accuracy of rate and thermal conductivity prediction.