Improved techniques for fluid diversion in oil recovery. Final report

Abstract

This report describes work performed during the third and final year of the project, 'Tmproved Techniques for Fluid Diversion in Oil Recovery." This project was directed at reducing water production and increasing oil recovery efficiency. In the United States, more than 20 billion barrels of water are produced each year during oilfield operations. An average of 7 barrels of water are produced for each barrel of oil. Today, the cost of water disposal is typically between $0.25 and $0.50 per bbl. Therefore, there is a tremendous economic incentive to reduce water production if that can be accomplished without sacrificing hydrocarbon production. Environmental considerations also provide a significant incentive to reduce water production during oilfield operations.This three-year project had two technical objectives. The first objective was to compare the effectiveness of gels in fluid diversion (water shutoff) with those of other types of processes. Several different types of fluid-diversion processes were compared, including those using gels , foams , emulsions, particulates, and microorganisms. The ultimate goals of these comparisons were to (1) establish which of these processes are most effective in a given application and (2) determine whether aspects of one process can be combined with those of other processes to improve performance. Analyses and experiments were performed to verify which materials are the most effective in entering and blocking high-permeability zones.The second objective of the project was to identify the mechanisms by which materials (particularly gels) selectively reduce permeability to water more than to oil. A capacity to reduce water permeability much more than oil or gas permeability is critical to the success of gel treatments in production wells if zones cannot be isolated during gel placement.Topics covered in this report include (1) determination of gel properties in fractures, (2) investigation of schemes to optimize gel placement in fractured systems, (3) an investigation of why some polymers and gels can reduce water permeability more than oil permeability, (4) consideration of whether microorganisms and particulates can exhibit placement properties that are superior to those of gels, and (5) examination of when foams may show placement properties that are superior to those of gels.This project received financial support from the U.S. Department of Energy, the State of New Mexico, and a consortium of 10 oil companies. The technology developed in this project was transferred to the oil industry in several ways. First, project review meetings were held regularly, with 27 people from 13 organizations attending the most recent review (August 15-16, 1995). Second, technical progress reports were issued quarterly and annually. Third, papers were regularly presented at meetings of the Society of Petroleum Engineers (SPE) and were published in SPE and other journals (see Appendix F). Fourth, in conjunction with SPE's Distinguished Lecture Series, the presentation, " Cost-Effect...

Aperture-Tolerant, Chemical-Based Methods to Reduce Channeling

“…[124][125][126][127][128]155,156 That is, they are NOT super-polymer flooding agents. In particular, researchers from the University of Kansas 125,126 , the University of TX 124 , and New Mexico Tech 156,157 found that resistance factors (effective viscosities) provided by aluminum-citrate-HPAM colloidal dispersion gels within cores (i.e., beyond the inlet core section) were the same as those provided by polymer solution alone (i.e., containing no crosslinker). This observation suggests that either the gel particles were too small to interact significantly with pore throats or the crosslinking reaction did not take place to a significant extent.…”

“…In other cases, 155,156 CDG gelants were found to penetrate into sand packs or sandstone and ultimately provide significant residual resistance factors. However, relatively short gelation times (less than one day) preclude deep penetration into reservoirs (i.e., over the course of weeks or months).…”

“…However, relatively short gelation times (less than one day) preclude deep penetration into reservoirs (i.e., over the course of weeks or months). 155,156 Parallel Corefloods Are a Poor Indicator of Diversion. Representing a vendor of the colloidal dispersion gels, Smith et al 117 argued in contradiction to the results published by the above independent laboratories.…”

“…If gelation is stopped sufficiently early or if gels are sufficiently sheared so that gel particles remain significantly smaller than pore throats, the gel suspensions can propagate through porous rock; however, the level of mobility reduction (residual resistance factor) is generally small (less than 2). 16 Independent studies at several locations (the University of Kansas, 125,126,155 the University of TX, 124 New Mexico Tech, 156,157 Stavanger College, 128 and BP 127 ) confirm that aluminum-citrate-HPAM gelants and gels behave like other gelants and gels.…”

Improved methods for water shutoff. Annual report, October 1, 1996--September 30, 1997

“…65 We wondered if the disproportionate permeability reduction varies with core length. To answer this question, we performed an oil-water experiment in a 2-ft Berea core.…”