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Collaborating Authors
Waterflooding
Abstract Poor injection water quality is a prime factor in the reduction in injectivity in many water injection and disposal wells. These reductions in injectivity often result in costly workovers, stimulation jobs and recompletions, or, in many cases, the uncontrolled fracturing of wells by high bottomhole pressures resulting in poor water injection conformance and reduced overall sweep efficiency and recovery. This paper discusses many commonly occurring water quality issues and how they impact injectivity, including damage due to injection of suspended solids, fines migration, clay swelling and deflocculation, formation dissolution, chemical adsorption and wettability alterations, relative permeability effects associated with the injection of skim oil or grease and the injection of entrained free gas, biologically and bacterially induced damage, formation of insoluble scales and precipitates, emulsification, wax and asphaltene deposition. Screening criteria are presented to allow for a rigorous evaluation of a particular injection water source to investigate potential areas of sensitivity and to attempt to minimize problems associated with impaired injectivity. Introduction Water injection processes are utilized throughout the world to dispose of produced aqueous fluids and as a means of increasing the recovery efficiency in many oil reservoirs. A key factor in the success of these operations is contingent on being able to inject a sufficient quantity of the water of interest into the target zone. Injectivity can be restricted by:Poor inherent reservoir quality; Insufficient pay or contact of the pay zone of interest by the injection well; Formation damage effects associated with the actual water injection process. The subject matter of this paper will concentrate on the topic of injection water quality and how this factor relates to impaired injectivity. Impaired injectivity causes problems in that it restricts the volume of water which can be injected in a given well (causing potential problems with voidage replacement for a waterflood, or the buildup on surface of a large volume of produced water in a disposal operation). Often downhole injection pressure may exceed fracture pressure causing the initiation and propagation of uncontrolled induced fractures. These fractures may reduce overall efficiency of the waterflood process by lowering areal sweep efficiency and possibly directing injected fluids out of the zones of interest. However, in some cases, fractures may provide connections to zones of interest. Almost all problems associated with impaired injectivity can ultimately be related back to problems associated with water quality. Potential damage mechanisms which can be associated with water injection processes include:Mechanically induced damage, including: a) Injection of solids, b) Velocity induced damage (fines migration) and settling, where fines are present Injection water/formation rock interactions, including: a) Clay swelling, b) Clay deflocculation, c) Formation dissolution, d) Chemical adsorption/wettability alterations. Relative permeability effects, including: a) Skim oil entrainment, b) Free gas entrainment. Biologically induced impairment, including: a) Bacterial entrainment and growth. Injection water/in situ fluid interactions, including: a) Formation of insoluble scales, b) Emulsification and emulsion blocks, c) Precipitation, d) Wax/asphaltene deposition.
- North America > United States > California (0.46)
- North America > Canada > Alberta (0.30)
- Water & Waste Management > Water Management > Lifecycle > Disposal/Injection (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Abstract Poor injection water quality is a prime factor in the reduction in injectivity in many water injection and disposal wells. These rejections in injectivity often result in costly workovers, stimulation jobs and recompletions or, in many cases, the uncontrolled fracturing of wells by high bottomhole pressures resulting in poor water injection conformance and reduced overall sweep efficiency and recovery. This paper discusses many commonly occurring water quality issues and how they impact injectivity, including damage due to injection of suspended solids, fines migration, clay swelling and deflocculation, formation dissolution, chemical adsorption and wettability alterations, relative permeability effects associated with the injection of skim oil or grease and the injection of entrained free gas, biologically and bacterially induced damage, formation of insoluble scales and precipitates, emulsification, Will: and asphaltene deposition. Screening criteria are presented to allow for a rigorous evaluation of a particular injection water source to investigate potential areas of sensitivity and to attempt to minimize problems associated with impaired injectivity. Introduction Water injection processes are utilized throughout the world to dispose of produced aqueous fluids and as a means of increasing the recovery efficiency in many oilreservoirs. A key factor in the success of these operations is contingent on being able to inject a sufficient quantity of the water of interest into the target zone. Injectivity can be restricted by:Poor inherent reservoir quality; Insufficient pay or contact of the pay zone of interest by the injection well; Formation damage effects associated with the actual water injection process. The subject matter of this paper will concentrate on the topic of injection water quality and how this factor relates to impaired injectivity. Impaired injectivity causes problems in that it restricts the volume of water which can be injected in a given well (causing potential problems with voidage replacement for a waterflood, or the buildup on surface of a large volume of produced water in a disposal operation). Often downhole injection pressure may exceed fracture pressure causing the initiation and propagation of uncontrolled induced fractures. These fractures reduce overall efficiency of the waterflood process by lowering areal sweep efficiency and possibly directing injected fluids out of the zones of interest. Almost all problems associated with impaired injectivity can ultimately be related back to problems associated with water quality. Potential damage mechanisms which can be associated with water injection processes include:Mechanically induced damage, including:Injection of solids Velocity induced damage (fines migration) Injection water-formation rock interactions, including:Clay swelling Clay deflocculation Formation dissolution Chemical adsorption/wettability alterations Relative permeability effects, including:Skim oil entrainment Free gas entrainment Biologically induced impairment, including:Bacterial entrainment and growth Injection water-insitu fluid interactions, including:Formation of insoluble scales Emulsification Precipitation Wax/asphaltene deposition Each of these phenom
- Water & Waste Management > Water Management > Lifecycle > Disposal/Injection (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Many factors affect the behavior of a waterflood. Using data from an actual reservoir, the effect of rate on recovery from sandstone reservoirs undergoing horizontal waterflooding is investigated. The study extends previous work by considering heterogeneous systems and by including the effect of capillary forces. Introduction The optimum rate of recovery from a given reservoir must be based on good conservation practice and on sound economic grounds. The optimum rate, or maximum efficient rate, for a reservoir can be defined in various ways, depending on the criterion used, For instance, optimum rate could be defined as that which gives the highest ultimate recovery or as that which gives the highest present-worth value. The optimum rates obtained using these two criteria could be considerably different. However, in defining a practical optimum rate, both economic and conservation practical optimum rate, both economic and conservation factors must be considered to arrive at a reasonable rate of recovery. Many factors affect the behavior of a waterflood. The significant factors over which the operator has little or no control are mobility ratio, heterogeneity, and wettability. Some of the important rate-dependent processes are imbibition, gravity segregation, and, in some cases, coning. These factors may all affect ultimate waterflood recoveries; however, do the rate-dependent parameters cause ultimate recovery to be rate sensitive? Recently, production rates have approached capacity in many reservoirs because of the rapidly increasing world-wide demand for crude oil. This has resulted in consider-able in-fill drilling for increased capacity, and has increased individual well rates to relatively high levels. Using existing literature, it is difficult to establish the influence of this rapid depletion rate on ultimate recovery. The rate-sensitivity question has been debated for the last 17 years. In the 1950's, laboratory models and field performance data were used to obtain some idea of the performance data were used to obtain some idea of the influence of rate on recovery. Field performance studies were inconclusive because of the difficulty in analyzing field data for predicting ultimate recovery under changing rate conditions. Laboratory-model results were difficult to correlate to field performance because of scaling problems. Most of these studies indicate that increases in rate result in less recovery for a given amount of water injected. However, these studies fail to show recovery at the economic limit. Jordan et al. concluded that higher rates were not necessary to obtain maximum recovery and speculated that, in heterogeneous systems, lower rates could possibly increase recovery because of capillary forces. There was, however, no evidence indicating that lower rates would actually increase ultimate economic recovery. More recently, Miller and Rogers investigated the rate-sensitivity problem for waterflooded sandstone reservoirs. They carried out 156 simulation runs to investigate the influence of eight performance variables on ultimate recovery by waterflooding. The performance variables investigated were (1) oil-zone thickness (5, 10, 40, 68, and 80 ft), (2) horizontal permeability (250, 750, and 1,500 md), (3) total gross fluid rates (400, 1,000, and 2,000 B/D), (4) perforated interval (12.5 and 100 percent of oil zone thickness), (5) ratio of water-zone percent of oil zone thickness), (5) ratio of water-zone thickness to oil-zone thickness (0.250, 0.875, 1.875, and 6.000), (6) kv/kh (0.1, 0.5, and 1.0), (7) mobility ratio (0.25, 1.00, 1.25, and 4.00), and (8) drainage area (10, 20, and 40 acres). JPT P. 555
- North America > Canada (0.29)
- Asia > Middle East > Jordan (0.24)
- Oceania > Australia > Victoria > Bass Strait > Gippsland Basin (0.93)
- North America > United States > Louisiana > Rogers Field (0.89)
- Europe > United Kingdom > North Sea > Central North Sea > South Viking Graben > Blocks 16/7b > Miller Field (0.89)
- Europe > United Kingdom > North Sea > Central North Sea > South Viking Graben > Block 16/8b > Miller Field (0.89)