Annual Research Reports - Randy Seright - US Department of Energy

This report describes work performed during the third and final year of the project, “Using Chemicals to Optimize Conformance Control In Fractured Reservoirs.” This research project had three objectives. The first objective was to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective was to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective was to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consisted of three tasks, each of which addressed one of the above objectives. Our work was directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

This report describes work performed during the second year of the project, “Using Chemicals to Optimize Conformance Control In Fractured Reservoirs.” This research project has three objectives. The first objective is to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective is to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective is to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consists of three tasks, each of which addresses one of the above objectives. Our work is directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

This report describes work performed during the first year of the project, “Using Chemicals to Optimize Conformance Control In Fractured Reservoirs.” This research project has three objectives. The first objective is to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective is to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective is to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consists of three tasks, each of which addresses one of the above objectives. Our work is directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

This final technical progress report summarizes work performed the project, “Use of Polymers to Recover Viscous Oil from Unconventional Reservoirs.” The objective of this three-year research project was to develop methods using water soluble polymers to recover viscous oil from unconventional reservoirs (i.e., on Alaska’s North Slope). The project had three technical tasks. First, limits were re-examined and redefined for where polymer flooding technology can be applied with respect to unfavorable displacements. Second, we tested existing and new polymers for effective polymer flooding of viscous oil, and we tested newly proposed mechanisms for oil
displacement by polymer solutions. Third, we examined novel methods of using polymer gels to improve sweep efficiency during recovery of unconventional viscous oil.

This technical progress report describes work performed from October 1, 2009, through September 30, 2010, for the second year of the project, “Use of Polymers to Recover Viscous Oil from Unconventional Reservoirs.” For HPAM (partially hydrolyzed polyacrylamide) solutions with a sufficiently low salinity (i.e., tap water or distilled water) and/or sufficiently high polymer concentration, shear thinning can be observed in porous media at moderate to low fluxes. However, under practical conditions where HPAM is used for EOR, the degree of shear thinning is slight or non-existent, especially compared to the level of shear thickening that occurs at high fluxes. Xanthan solutions are well known to exhibit shear thinning both in viscometers and in porous media. Contrary to recent suggestions in the literature, shear thinning by polymer solutions is shown not to be a significant liability for vertical sweep efficiency. The overall viscosity (resistance factor) of the polymer solution is of far greater relevance than the rheology.
Contrary to earlier claims, permeability reduction associated with polymers is shown not to benefit vertical sweep efficiency during polymer flooding.

This technical progress report describes work performed from October 1, 2008, through September 30, 2009, for the project, “Use Of Polymers To Recover Viscous Oil From Unconventional Reservoirs.” Fractional flow calculations were performed to examine the potential of polymer flooding for a range of characteristics in viscous oil reservoirs (especially relevant to the North Slope of Alaska). Using these recovery results, a simple economic analysis was performed to make a preliminary assessment of the potential for polymer flooding in reservoirs with viscous oils. The analysis indicated that over a significant range of throughput values, polymer flooding can provide a higher relative profit than waterflooding. The results emphasize that maximizing injectivity of polymer solutions may be key to economic implementation of polymer flooding for recovery of viscous oils.

This report describes work performed during the third year of the project Improved Techniques for Fluid Diversion in Oil Recovery. This three-year project has two general objectives. The first objective is to compare the effectiveness of gels in fluid diversion with those of other types of processes. Several different types pf fluid-diversion processes are being compared, including those using gels, foams, emulsions and particulates. The second objective is to identify the mechanisms by which materials (particularly gels) selectively reduce permeability to water more than to oil.

This report describes work performed during the second year of the project Improved Techniques for Fluid Diversion in Oil Recovery. This three-year project has two general objectives. The first objective is to compare the effectiveness of gels in fluid diversion with those of other types of processes. Several different types pf fluid-diversion processes are being compared, including those using gels, foams, emulsions and particulates. The second objective is to identify the mechanisms by which materials (particularly gels) selectively reduce permeability to water more than to oil.

This report describes work performed during the first year of the project Improved Techniques for Fluid Diversion in Oil Recovery. This three-year project has two general objectives. The first objective is to compare the effectiveness of gels in fluid diversion with those of other types of processes. Several different types pf fluid-diversion processes are being compared, including those using gels, foams, emulsions and particulates. The second objective is to identify the mechanisms by which materials (particularly gels) selectively reduce permeability to water more than to oil.

This report describes work performed during the third and final period of the project, “Improved Methods for Water Shutoff.” This project had three general objectives. The first objective was to identify chemical blocking agents that will (a) during placement, flow readily through fractures without penetrating significantly into porous rock and without “screening out” or developing excessive pressure gradients and (b) at a predictable and controllable time, become immobile and resist breakdown upon exposure to moderate to high pressure gradients. The second objective was to identify schemes that optimize placement of the above blocking agents. The third objective was to explain why gels and other chemical blocking agents reduce permeability to one phase (e.g., water) more than that to another phase (e.g., oil or gas). We also wanted to identify conditions that maximize this phenomenon.

This report describes work performed during the second period of the project, “Improved Methods for Water Shutoff.” This project has three general objectives. The first objective is to identify chemical blocking agents that will (a) during placement, flow readily through fractures without penetrating significantly into porous rock and without “screening out” or developing excessive pressure gradients and (b) at a predictable and controllable time, become immobile and resist breakdown upon exposure to moderate to high pressure gradients. The second objective is to identify schemes that optimize placement of the above blocking agents. The third objective is to explain why gels and other chemical blocking agents reduce permeability to one phase (e.g., water) more than that of another phase (e.g., oil or gas). We also want to identify conditions that maximize this phenomenon.

This report describes work performed during the first period of the project, “Improved Methods for Water Shutoff.” This project has three general objectives. The first objective is to identify chemical blocking agents that will (a) during placement, flow readily through fractures, small casing leaks, and narrow channels behind pipe without penetrating significantly into porous rock and without “screening out” or developing excessive pressure gradients and (b) at a predictable and controllable time, become immobile and resist breakdown upon exposure to moderate to high pressure gradients. The second objective is to identify schemes that optimize placement of the above blocking agents. The third objective is to explain why gels and other chemical blocking agents reduce permeability to one phase (e.g., water) more than that of another phase (e.g., oil or gas). We also want to identify conditions that maximize this phenomenon.

This report describes progress made during the third and final year of the three-year project, “Fluid Diversion and Sweep Improvement with Chemical Gels in Oil Recovery Processes.” Our experimental work focused on four types of gels:
(1) resorcinol-formaldehyde,
(2) colloidal silica,
(3) Cr³⁺(chloride)-xanthan, and
(4) Cr³⁺(acetate)-polyacrylamide.

All experiments were performed at 41°C. During injection of gelants that contained Cr³⁺, chromium propagation was significantly more rapid when the counterion was acetate rather than chloride. For a given counterion, chromium propagation was much more rapid in Berea sandstone cores than in Indiana limestone cores. It is doubtful that unbuffered chromium-chloride gelants can propagate through carbonate reservoirs.

This report describes progress made during the second year of the three-year project, “Fluid Diversion and Sweep Improvement with Chemical Gels in Oil Recovery Processes.” The objectives of this project are to identify the mechanisms by which gel treatments divert fluids in reservoirs and to establish where and how gel treatments are best applied. Several different types of gelants are being examined. This research is directed at gel applications in water injection wells, in production wells, and in high-pressure gasfloods. The work examines how the flow properties of gels and gelling agents are influenced by permeability, lithology, and wettability. Other goals include determining the proper placement of gelants, the stability of in-place gels, and the types of gels required for the various oil recovery processes and for different scales of reservoir heterogeneity.

This report describes progress made during the first year of the three-year project, “Fluid Diversion and Sweep Improvement with Chemical Gels in Oil Recovery Processes.” The objectives of this project are to identify the mechanisms by which gel treatments divert fluids in reservoirs and to establish where and how gel treatments are best applied. Several different types of gelants are being examined, including a monomer-based gelant, several polymer-based gelants, and a colloidal silica gelant.

This report describes work performed during the second year of the project, “Conformance Improvement Using Gels.” The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.
Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil.

This report describes work performed during the first year of the project, “Conformance Improvement Using Gels.” The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

This technical progress report describes work performed from October 1, 2005, through September 30, 2006, for the project, “Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling.”

This technical progress report describes work performed from October 1, 2004, through September 30, 2005, for the project, “Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling.”