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Water produced with crude oil can successfully be reclaimed for use as oilfield steam generator feed-water. Getty Oil Company in the Kern River Field near Bakersfield, California, reclaims and clarifies 80,000 cubic meters of produced water per day for use as steam generator feedwater.
Getty Oil Company in the Kern River Field employs tertiary thermal steamflooding methods to produce 13 degrees API gravity crude from depths of 300 meters. Approximately 230 oilfield steam generators consisting of 6 and 15 megawatt models are used to provide steam for this operation. Feedwater demand is 80,000 cubic meters per day and is expected to increase another 30 percent when the field is fully expanded. percent when the field is fully expanded. Because of the arid climate of Bakersfield, California, the most available and economical source of steam generator feedwater is the fresh water which is produced with the crude oil. Recycling the produced water also minimizes disposal problems. For produced water also minimizes disposal problems. For each cubic meter of oil, nine cubic meters of water are produced. However, before this produced water can be used for feedwater, the residual oil, suspended solids and hardness must be removed. Getty Oil Company in the Kern River Field has designed and built a reclamation facility for this purpose.
PROCESS DESCRIPTION AND THEORY PROCESS DESCRIPTION AND THEORY The facility employs chemical treating, mechanically induced and dissolved gas flotation, sedimentation, and pressure cake filtration to remove suspended solids and oil in the produced water. Following these processes, sodium zeolite cation exchange softeners are used to remove hardness. A process line diagram is shown in Figure 1.
Reclamation of the produced water begins after initial gravity oil-water separation has reduced insoluble oil and suspended solids to approximately 200 milligrams per kilogram each. Table 1 presents water analyses of the produced water before and after the reclamation process. The first process utilizes an oilfield depurator unit which mechanically induces flotation air to reduce oil and suspended solids to 20 and 100 milligrams per kilogram, respectively. Mechanically induced air flotation is accomplished in the depurator unit using a motor-driven rotor mechanism which pulls air or gas into a cell with the produced water. The resulting shearing forces cause the produced water. The resulting shearing forces cause the gas to form minute bubbles which attach to oil particles and suspended solids as they rise to the particles and suspended solids as they rise to the surface. A dense froth is formed on the surface and the oil and solids are removed from the cell by skimmer paddles. paddles. Following the depurator units, the produced water flows through a 122 centimeter pipeline to sedimentation basins where chemical treating with reverse emulsion breakers and polymer coagulants are added to break out and agglomerate oil. Some of the suspended solids also drop out during the sedimentation period. Produced water discharged from these basins then Produced water discharged from these basins then contains 10 milligrams per kilogram insoluble oil and 80 milligrams per kilogram suspended solids. These basins also provide important surge capacity as the inlet produced water volume can vary over 16,000 cubic meters produced water volume can vary over 16,000 cubic meters of water per day.
The discharge of the sedimentation basins to the physical plant inlet is through a 91-centimeter line physical plant inlet is through a 91-centimeter line to pumps which charge dissolved gas flotation cells. Nitrogen gas is introduced into the produced water stream through eductors on the cell charge pumps. The nitrogen is stored as a liquid at a nearby site and is vaporized and automatically supplied to the plant upon demand. The nitrogen dissolves into plant upon demand. The nitrogen dissolves into minute bubbles which then contact oil particles and suspended solids. The oil and solids are lifted to the surface in the flotation cells and are skimmed off. This process reduces insoluble oil and suspended solids to 5 and 50 milligrams per kilogram, respectively. The cells then discharge to a holding tank prior to the filtering process.
Abstract Introduction Unaccounted for solids deposition in oil and gas wells can significantly impact production rates and overall well performance. This study evaluates the impact of including a solid slow-release scale inhibitor in the stimulation package as it relates to production enhancement. While this study focuses on the Eagle Ford in LaSalle and McMullen Counties, correlations to similar formations can be made. The Eagle Ford shale is recognized as a prolific unconventional play that has very dynamic production challenges. Many issues can be experienced shortly into the life of the well, although observable scale does not manifest early on in many cases. Application A major Eagle Ford operator saw a financial and operational benefit in establishing long-term scale treatment with a single application. The operator opted to use this solid inhibitor to extend the treatment life, to reduce subsequent intervention costs for solids removal, and to maintain proppant conductivity. Through the application of this solid chemical, the operator was able to place the inhibitor deep in the fractured formation before the first instances of pressure and temperature changes. The particle slowly releases the adsorbed scale inhibitor into the bulk water as it flows through the propped zone, providing immediate and long-term protection against solids deposition. Solids deposition can restrict production pathways through the proppant pack, contributing to loss of conductivity. Results, Observations, and Conclusions Through the use of empirical data, this paper describes the relationship between an increase in total dissolved solids in produced water to an increase in production when compared to untreated wells. Post-stimulation monitoring of treated and untreated wells show a substantial differential in water composition, indicating that when left untreated, solids are precipitating in unseen places like the proppant pack and perforations. The operator has been able to operate more efficiently and show an increase in production while saving valuable time and cost on scale remediation during the well's life. Significance of Subject Matter While it is understood that there are multiple contributors affecting a well's production, mitigating solids deposition in the proppant pack plays a substantial role. Removing solids from the well can reduce damage to the proppant conductivity and result in production enhancement.
The value of water analysis data in petroleum exploration and production iswidely recognized. Water analyses have proven useful in water productionproblems, in the correlation of stratigraphic units and of the aquifers withinthese units, and in the study of the movement of subsurface waters.
A large volume of water analysis data is available for the Western CanadaSedimentary Basin. Maximum benefits may be derived from these data through thecareful selection of analyses that represent most accurately the chemicalcomposition of the subsurface waters.
Various graphical methods have been devised for presenting the chemicalanalysis of a water. Graphical diagrams are particularly useful in comparingwater analyses.
Isoconcentration maps provide information essential for the study of thechemical and physical behaviour of formation waters. Furthermore, these mapsprovide information that can be converted readily to water resistivitydata.
Studies of the chemistry of formation waters, carried out in conjunctionwith studies of the geologic framework wherein the waters reside, can be mosteffective in the solution of local and regional problems.
American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.
A method of programmed data acquisition is presented to help non-specialist engineers monitor water quality. Field tests, sample collection, laboratory procedures and methods of data presentation are standardized. Specifically, a series of profile plots are prepared from which engineers "read-out" pertinent features of plant performance and water quality. The direct "read-out" procedure, after nominal practice, is relatively simple. In many respects, it may be compared with qualitative log interpretation.
A manual for using the Standard Data Package is also presented. Included are "rules of thumb" and other empirically derived "yardsticks" covering several important parameters.
The increasing importance of salt water handling, either in disposal or waterflood operations, has demanded development of better methods. A full understanding of basic parameters is fundamental to creating the best plant design and to determining the most effective operating practices. Toward this end various methods have been proposed to define "water quality", diagnose problems, predict potential problems and ultimately, to use these technical method to maximize operating efficiency.
It is a major purpose of this paper to present a standardized method of programmed data acquisition that lends itself to direct measurement of water quality by non-specialist engineers. The heart of the program is the collection and preparation of a "Standard Data Package". While involving a comprehensive technical investigation, the interpretation process is simplified so that unusual technical skills are not often required.
Specifically, a standardized format is proposed whereby engineers can inspect a series of charts and "read-out" pertinent features of an injection system's performance. While the "read-out" process appears quite simple, the individual is in effect solving partial chemical material balance calculations that logically lead to sound engineering conclusions.
The standardized plan is readily adaptable to regular surveillance of water systems. After an initial comprehensive study, data acquisition can be programmed in advance so that attention is focused on an operation at regular intervals. Comparison of standard charts of succeeding studies is done by inspection. Likewise, with all procedures standardized, results between studies of different projects can be directly compared.
The proposed plan of water quality control can be illustrated by noting the physical similarity of water injection systems and chemical manufacturing plants. Both convert raw material to finished products. Either may be simple or highly complex. Systematic collection of basic in-put and out-put data is recognized as a requirement for efficient operation of a manufacturing plant.
Abstract Potential risks to livestock may occur if they are exposed to releases of petroleum hydrocarbons at or near oil production facilities. In 2004, the American Petroleum Institute (API) published Risk Based Screening Levels for the Protection of Livestock Exposed to Petroleum Hydrocarbons . The API framework, conceptual site model, and screening-level procedures were used in a case study to evaluate potential risks to livestock at the oilfield sites in northeastern Ecuador. API's toxicity reference values (TRVs) as well as their drinking water and soil risk-based screening levels (RBSLs) for livestock were used to evaluate whether levels of hydrocarbons in soil and water could pose a health risk to cattle, calves, sheep, goats, or horses. RBSLs are threshold concentrations in site media (e.g. soil, water, and air) below which no significant unacceptable risks to livestock are expected. Since pigs, chickens, and ducks are also commonly raised in northeastern Ecuador, new TRVs were calculated for them based on a review of all published toxicity values. RBSLs for pigs, chickens, and ducks were then calculated using exposure assumptions aligned with API's conceptual site model. The evaluation presented herein was a screening-level risk assessment using a conservative approach to evaluate potential risks to livestock from exposure to petroleum at the oilfield sites. The RBSLs and TRVs were conservative because they are based on non-lethal endpoints protective of individual livestock, and the mammalian RBSLs for TPH were based on fresh crude oil rather than on the weathered, less toxic oil that is typically found in soils in tropical climates. In this case study, data from over 300 surface soil and 100 surface water samples from seven oilfields in northeastern Ecuador were collected during field inspections conducted from 2004 through 2006. Potential hydrocarbons of concern included: crude oil or total petroleum hydrocarbons (TPH); benzene, toluene, ethylbenzene, and xylene (BTEX); and polycyclic aromatic hydrocarbons (PAHs). Introduction The purpose of this case study was to evaluate claims of potential impacts to livestock in the northern Amazon region of Ecuador. The study area, shown in Figure 1, is an active oilfield concession area currently operated by Petroecuador (beginning in 1990) and formerly operated by Texaco Petroleum Company. Risks to livestock may occur if they are exposed to releases of petroleum hydrocarbons at or near oil production facilities. To address this potential risk, the American Petroleum Institute (API) developed conservative threshold values for petroleum hydrocarbons that can be used to characterize risks to livestock across a variety of conditions. In 2004, API published their Risk Based Screening Levels for the Protection of Livestock Exposed to Petroleum Hydrocarbons . API developed toxicity reference values (TRVs) and soil and water risk-based screening levels (RBSLs) for evaluating risks to cattle, calves, sheep, goats, and horses. In this study, additional TRVs and RBSLs were developed for pigs, chickens, and ducks following the established API framework.