Free Water Knockout Research Articles

Development of free water knock-out tank by using internal heat exchanger for heavy crude oil

Reactivation of an old oil well can be explicitly calculated to maximize crude oil production. The biggest challenge with the activation process is the crude oil content in old wells, which is not feasible to meet the specified minimum standards. In the case of the Bunian oil field, Indonesia, the crude oil produced has high water content. It causes a decrease in the quality of production and also hinders production capacity. The production scheme applied to the Bunian field has a storage tank that functions to reduce water content using the gravity method, but this is less effective. Let’s modify the storage tank into a heat exchanger tank through the engineering design process and labeled it as a free water knockout tank (FWKO). The FWKO is made of a multi-pass tube heat exchanger. The experiments are conducted through three phases’ tests before deciding the final design. From the test, the change in water content is varied with temperature differences of the working fluid and crude oil. The lowest water content is obtained at 0.5 % at final tests. After analyzing the characteristic of each test result, the final design is taken by adjusting the suitable working fluid temperature and pressure. Finally, by using suitable parameters, the average water content of crude oil is decreased up to the minimum requirement (<0.1 %). The design of FWKO is considered simple with an excellent performance and can adapted easily. The FWKO able to process crude oil with water content <20 %, where it suitable for waxy oil well. The working fluid can be processed both in liquid and gas state. Furthermore, the heating source for the working fluid is gained from the gas flare by using thermic heater. Thus, it does not require an extra heating source for the heat exchanger

Simulations of the Crude Oil Tank Refurbishment Project Risks Using Monte Carlo

Simulation technology has assisted project stakeholders in predicting a range of the project results in the future under risks and uncertainties. The objectives of this article are to improve a comprehensive project planning in the perspective of the project scheduling by conducting simulations for the refurbishment of crude oil tank project risks using Monte Carlo simulations. The practical approaches for simulating the risks encompassed 3 stages: risk identification, assessment, and risk analysis using the Monte Carlo simulations. The implementation of Monte Carlo simulation in the form of stochastic approach however were not new, but the application of these approaches in the area of oil industrial projects was challenging. A Free Water Knock-Out (FWKO) tank project located in Duri, Indonesia was taken as a case study. The initial FWKO project duration was set up to be 180 working days, and it was delayed (up to 140% from the initial duration of the project planning). This study conducted deep questioner surveys from 25 oil industry stakeholders. It was identified 29 risk factors have been considered as the major causes of the project delay. The risk factors were then calculated qualitatively for performing risk indexes. Based on the risk simulations (after 1000 iterations) using Monte Carlo simulations utilizing @risk application package (under uncertainties) there was found that the possibility of this project would experience delays at the range of 47 days (126%) to 80 days (144%) from the initial project planning. This simulation had also identified the most sensitive activities causing project delays. The results was presented in the form of the spider graph diagram which assisted the project main stakeholders in developing a strategic decision during project planning phase.

Мобильная установка предварительного сброса воды: опыт и достижения

Мобильная установка предварительного сброса воды: опыт и достижения

Understanding the effect of skim oil recycle on the water/oil separation in steam assisted gravity drainage operations

In steam assisted gravity drainage (SAGD) operations, skim oil recycled to a free water knockout (FWKO) often results in poor water quality and rag formation at the oil/water interface. To improve water quality and demulsification efficiency in the presence of skim oil recycle, it is necessary to understand the status of oil and solids in the produced water throughout the process. In this paper, the effect of skim oil on the water/oil separation in SAGD operations was studied. Dynamic optical fluid imaging (DOFI) technology was used to characterize oil and solids concentrations, oil droplet sizes, and the associated size distributions in the produced water collected from various vessels in a SAGD process. The DOFI analyses show that skim oil recycle caused more oil and solids to be sent to the FWKO, treater and induced gas flotation (IGF) outlet waters and finally to oil removal filters (ORF). The increased oil in water led to more oil droplets, especially more numerous small oil droplets remaining in the produced water. These small oil droplets are more challenging to remove than larger oil droplets, resulting in deteriorated water quality. Skim oil recycle decreased the oil removal efficiency of the IGF vessel and increased fouling of ORF filters by oil and solids. Fourier transform infrared spectroscopy analysis of the solids collected from the produced water in the presence of skim oil recycle indicated that the solids are bitumen-coated fine quartz and clays. Demulsification studies show that application of dual reverse emulsion breakers could help improve water quality and alleviate the negative effects due to the solids from skim oil addition.

Case History of Dehydration-Technology Improvement for HCPF Production in the Daqing Oil Field

Summary High-concentration polymer flooding (HCPF) is an enhanced-oil-recovery (EOR) method that has been used since conventional polymer flooding was applied in the main reservoirs of the Daqing oil field because its higher viscoelasticity can improve the oil-displacement efficiency. However, as a result of more produced hydrolyzed polyacrylamide (HPAM), the oil/water mixture is emulsified easily and separated with more difficulty. In this work, a case history of dehydration technology for HCPF production in the Daqing oil field is reviewed, and a laboratory investigation to assess the emulsification behaviors of HCPF-produced emulsions is conducted. Besides the dehydration-mechanism description of a high-voltage pulsed electrical field, electrostatic-demulsification performance for produced liquid from HCPF production is improved, and the operation parameters are optimized. Recent actual acceptance of the optimization recommendations is presented, and the field-application results are also discussed. The results indicate that dehydration technology for the Daqing oil field has been innovated with the industrialization of the EOR process. Traditional methods of gravity or centrifugal settling are replaced; this upgraded freewater knockout (FWKO) has the functions of adsorption, wetting, collision and coalescence, and oil pretreating for HCPF production. Because it is dominated by periodic vibration as its main mechanism, the pulsed-direct-current (DC) electrostatic-demulsification technique has some advantages in overcoming the obstacles encountered by regular types of electrical-field dehydration processes at strong emulsification stability. Compared with previous dehydration processes having complex alternating-current (AC)/DC electrical fields, the process with a pulsed-DC electrical field shows a unique advantage in terms of emulsified water-separation efficiency, energy conservation, environmental protection, lower labor intensity, and more-stable operation, and the dehydration performance meets the oil-treating standards. As the surface-matching technology of EOR, this improvement in dehydration technology is significant for promoting the construction of an HCPF demonstration project and accelerating petroleum development and production efficiently.

Case Study--Calcium-Carbonate-Scale Inhibitor Performance Degradation Because of H2S-Scavenger Injection in Semoga Field

Summary Semoga field is an oil field in the Rimau block, which is located in South Sumatra, Indonesia. There is also a nearby oil field, Kaji field, in this block. These fields experienced reservoir souring and suffered a history of calcium-carbonate (CaCO3) -scale cases before a proper scale-inhibition program was implemented. At the end of January 2011, there was a separation-system problem at free water knock-out (FWKO) #2 Semoga Station. FWKO outlet lines were dismantled for inspection purposes, and it was found that the oil-outlet line at the downstream of the level control valve (LCV) was clogged by deposits, leaving an inner diameter (ID) of only 0.5 in. X-ray defraction (XRD) and X-ray fluorescence (XRF) analyses confirm that the deposit is CaCO3 scale, even though routine scale-coupon monitoring shows very low scale growth. There is a hydrogen sulfide (H2S) scavenger Brand X injection at the downstream of the LCV on the FWKO #2, with a concentration of 11,050 ppm. The scale-inhibitor dosage in the water line on Semoga Station was only 9-10 ppm. Laboratory simulation shows that H2S scavenger Brand X injection reduced the scale-inhibition percentage from 97.2 to 35.3%, with 9 ppm of scale inhibitor. Meanwhile, no deposits were found in the oil-outlet line at the downstream of the LCV at Kaji Station, which has the same H2S scavenger-injection point and dosage. The scale-inhibitor dosage in the water line at Kaji Station was 17.5-22 ppm. Laboratory simulation shows that 20 ppm of scale inhibitor resulted in a scaleinhibition percentage of 58%. Laboratory analysis shows that the scale-inhibition percentage increases linearly as the scale inhibitor increases under H2S scavenger Brand X influence. However, another laboratory test conducted using H2S scavenger Brand Y shows that the scale-inhibition percentage will decrease with the increase of scale inhibitor concentration, until it reaches the lowest value before increasing again with the increase of scale inhibitor concentration. Thus, the scale-inhibitor performance under H2S scavenger Brand Y influence behaves parabolically. It is concluded that H2S-scavenger injection increases system pH, resulting in the increase of scaling tendency. However, adding scale-inhibitor concentration is not always the answer to overcoming scale growth resulting from this effect. It is important to understand scale-inhibitor performance behavior on certain H2S scavenger brands before taking preventive measures. Scale-inhibitor performance might have a linear correlation between increasing concentration and scale-inhibition percentage, as shown by the behavior with H2S scavenger Brand X, but it might also have a parabolic correlation, as shown by the behavior with H2S scavenger Brand Y or even other correlation types.

FWKO 유수분리공정을 이용한 오일-물 혼합물의 분리특성

오일-물 혼합물에서 물을 제거하기 위하여 FWKO(Free Water Knock Out) vessel에서의 물 분리특성에 대해 연구하였다. 오일을 모사하기 위해 데칸, 톨루엔, 아스팔트를 사용하였다. 데칸을 이용하여 프로토타입 vessel에서 기초실험을 수행하였으며, 기초실험결과를 토대로 최적 water cut이 0.8인 것을 알게 되었다. 이에 이어 톨루엔을 이용하여 성능평가를 실행한 결과로 최적 체류시간이 1,200 sec인 것을 알 수 있었고 아스팔트를 사용하여 방해판의 개수, 실험온도를 변수로 FWKO vessel에서의 최적의 물 분리조건에 대해 조사하였다. 최적의 분리조건은 방해판 3개, 온도 <TEX>$45^{\circ}C$</TEX>였다. Characteristics of water separation in a FWKO(Free Water Knok Out) vessel was investigated to remove water from oil-water mixture. Decane, toluene, and asphalt were used as model oils. Preliminary experiments were carried out for decane in a prototype FWKO vessel. Based on the results of preliminary experiments, the prototype vessel was modified and its performance was evaluated by using toluene. The effects of experimental variables on the separation of oil-water mixture were evaluated in terms of separation efficiency. The experimental variables include water cut(water ratio), number of baffles, residence times, and operation temperatures. The optimum conditions of water separation were found to be 0.8 water cut, 3 baffles, 1,200 sec, and <TEX>$45^{\circ}C$</TEX>.

Performance and Control of Liquid-Liquid Cylindrical Cyclone Separators

The feasibility of using liquid-liquid cylindrical cyclone (LLCC©) as a free-water knockout device for bulk separation of oil-water mixtures in the field strongly depends on the implementation of control systems due to its compactness, less residence time, and possible inlet flow variations. In this investigation, the LLCC control dynamics have been studied extensively both theoretically and experimentally. A linear model has been developed for the first time for LLCC separators equipped with underflow watercut control, which enables simulation of the system dynamic behavior. A unique “direct” control strategy is developed and implemented, capable of obtaining clear water in the underflow line and maintaining maximum underflow rate. Dedicated control system simulations are conducted using MATLAB/SIMULINK® software to simulate the real system dynamic behavior. Detailed experimental investigations are conducted to evaluate the system sensitivity and dynamic behavior of the proposed control strategy. The results demonstrate that the proposed control system is capable of controlling the underflow watercut around its set point by obtaining maximum free-water knockout for a wide range of flow conditions, namely, inlet water concentration of 40% to 95% and inlet mixture velocity of 0.2 m/s to 1.5 m/s.

Oil-Water Separation in a Novel Liquid-Liquid Cylindrical Cyclone (LLCC©) Compact Separator—Experiments and Modeling

The hydrodynamics of multiphase flow in a Liquid-Liquid Cylindrical Cyclone (LLCC) compact separator have been studied experimentally and theoretically for evaluation of its performance as a free water knockout device. In the LLCC, no complete oil-water separation occurs. Rather, it performs as a free-water knockout, delivering a clean water stream in the underflow and an oil rich stream in the overflow. A total of 260 runs have been conducted, measuring the LLCC separation efficiency for water-dominated flow conditions. For all runs, an optimal split-ratio (underflow to inlet flow rate ratio) exists, where the flow rate in the water stream is maximum, with 100% watercut. The value of the optimal split-ratio depends upon the existing inlet flow pattern, and varies between 60% and 20%. For split-ratios higher than the optimal one, the watercut in the underflow stream decreases as the split-ratio increases. A novel mechanistic model has been developed for the prediction of the complex flow behavior and the separation efficiency in the LLCC. Comparisons between the experimental data and the LLCC model predictions show excellent agreement. The model is capable of predicting both the trend of the experimental data as well as the absolute measured values. The developed model can be utilized for the design and performance analysis of the LLCC.

Application of EOS to Optimize the Design of an Early Production Scheme of an Onshore Oil Field in Abu Dhabi.

This study is aimed at optimizing the design of surface facilities of an early production scheme for an onshore Abu Dhabi oil field. The current design of separation facilities is modular, and thus improvements in performance are possible with a better understanding of PVT properties of the oil produced. This is performed by optimizing the multistage separator process for the range of properties of oil processed by the facilities.This paper describes the characterization of the crude oil processed by the facility using the 3-parameter Peng-Robinson Equations of state to describe the phase behavior and fluid properties using reservoir fluid data and an analysis of production data. After characterizing the fluids from each production well in the reservoir, the streams are mixed and the overall characterization of the total reservoir crude oil is used to optimize the design of the current facilities. This overall characterization of the crude oil is checked and compared to field analysis from the current operating facility.Current production facilities consist of one production separator followed by a free water knockout tank. Results show that optimum separation requires a multi-stage scheme versus the two-stage scheme being used now. Up to 2-3% increase in oil volumes produced may be achieved by using an optimized 3-stage separator design consisting of high and medium pressure production separators followed by the free water knockout tank.

Analysis off Gravity Separation in Freewater Knockouts

Summary The selection of a freewater knockout depends on the desired performance. The design criterion developed here is based on the perception that most FWKO's are installed to remove the bulk of the water from a high-water-cut flow stream so that the oil can be dehydrated economically to salable specifications and to discharge water requiring minimal treatment before disposal. Only the gravity separation process is considered; the contribution of coalescing devices is excluded. Vertical FWKO's are discussed briefly, but the bulk of this paper is devoted to horizontal FWKO's, which constitute a majority of vessels. Hydraulic similarity of horizontal FWKO's and API separators is demonstrated, and a design criterion for FWKO's is developed with the basis used in the design development for API separators. This analysis discloses that commonly used criteria overrate the ideal flow capacity of FWKO's by a factor of 4/π. It shows that maximum FWKO capacity occurs when the oil/water interface is maintained at a level of 0.769 diameters in the case of ideal vessels and somewhat higher for nonideal vessels, rather than 0.50 as commonly believed. Published FWKO residence-time distributions (RTD's) indicate nonideal flow. Consequently, a design allowance for short-circuiting and turbulence effects was incorporated into the FWKO design. The effect of vessel proportions on cost per unit capacity is analyzed and an equation is developed for determining optimum proportions.

Oil Removal From Oilfield-Produced Water By Cross Flow Ultrafiltration

Abstract The technical and economic viability has been determined for crass flow ultrafiltration of oilfield-produced water with the goal of producing oil-free water for steam generation. Experiments with produced water supplied from various oil producing sites of western Canada have been performed with successful permeation rates and permeate quality. The resistance to membrane fouling and other factors that decrease permeation rate have been determined in long-term experiments. These results have been used to prepare a cost survey of the cross flow ultrafiltration process, and this has been compared to conventional treatment. The results indicate the level of performance that must be maintained in the ultrafiltration process to be economically advantageous. Introduction Enhanced oil recovery (EOR) operations in western Canada often employ stearn to stimulate reservoirs. These steam stimulation operations require large volumes of water for steam generation and injection into the oil-bearing reservoirs. They generate large volumes of produced water which is contaminated with oil, dissolved organic compounds, and inorganic material(1). Because many recovery operations in western Canada are located in water deficient or environmentally sensitive areas, several EOR recovery operations are recycling a portion of their produced water. Oilfield steam boilers that generate 80% quality steam (80% Vapour, 20% liquid) can tolerate minor amounts of total dissolved solids (TDS), hardness, and silica, but require total removal of the oil(2). Conventional treatment for the removal of the oil is limited by the presence of very stable oil-in-water (o/w) emulsions, stabilized by the presence of natural or added surfactants(3, 4). As well, subsequent operations of silica removal and softening perform best when the oil has been removed. Some EOR operations use large amounts of water, sometimes as much as 2 m3 to 10 m3 for every cubic metre of recovered oil. Some of this water may be present in the recovered oil as a water-in- oil emulsion while the balance may be present as a distinct water phase with an o/w emulsion. The produced fluid is generally treated in a free water knock out (FWKO) tank and a high-temperature separator (HTS) to separate as much of the oil and water as possible. Water from the FWKO and HTS is usually combined and sent to a skim tank where some residual oil is removed and recycled to the oil recovery part of the process. The remaining water, with some oil, is often disposed of by deep well injection (below the oil bearing formation) or it is sent to further treatment to prepare it for steam generation. Further treatment may consist of final oil removal by induced gas flotation (IGF) and filtration followed by softening operations such as hot lime softening and ion exchange. All of the oil removal operations with the exception of FWKO require large amounts of demulsifying chemicals to destabilize the emulsions. Occasional process upsets and changes in the nature of the emulsions can cause the failure of these units to remove oil from the produced water, and results in the passage of slugs of oil with catastrophic effects on the subsequent de-oiling and water softening operations.

Optimizations in the Design and Operation of an Offshore Hydraulic Pumping System

This paper presents an overview of the design and operation of an offshore hydraulic pumping system on Platform Eve when it was converted from a power-oil to a power-water system in 1983. Also described are some useful economic and operational data obtained from experience with hydraulic pumping systems over several years of operation.

Design and Operation of a 160,000-BFPD Centralized Production and Injection Scheme at Weyburn

Abstract Unitization of the Weyburn Oilfield was necessary to facilitatewaterflooding the limestone producing formation. At its inception, on July 1,1963, the Unit comprised 550 wells producing through 115 tank batteries. Underunitized operation, advantage was taken of the unrestricted market for oil andthe removal of regulatory production restrictions, permitting productionpractice on a maximum- efficient-rate basis. Production facilities wereconsolidated and injection facilities installed, so that emulsion treating andinjection water pumping are concentrated at one centrally located plant. This paper describes the design criteria and the operating experience of thecentralized production and injection scheme from March, 1964, to date. Adescription is given of the pre-unit operation and equipment, and of the designconsiderations to convert to an optimum gathering system through test and groupsatellites to a central treating plant. The reasons for the choice of one plantrather than several are outlined. The design of the emulsion flow streamthrough heat exchangers, free water knockout vessels, a flow splitter, fourhorizontal heater treaters and finally to three storage tanks is presented. Theselection of the source water supply and equipment, and the sizing ofhigh-pressure water pumps and gas engine drives are discussed, as well as thecorrosion-protected, radial water injection system. The alternatives consideredfor the large-size artificial lift equipment installed on producing wells aregiven. Comments on equipment performance and costs are made. Introduction The Weyburn Oilfield is located 85 miles south and east of Regina, Saskatchewan (Figure1). The producing zone is comprised of the Mississippian Midale beds, which lie at an average depth of 4,600 ft fromsurface. On July 1, 1963, 53 owners of 550 wells consolidated their operationsby unitizing 70 sq. miles of productive oil land, and appointed Central-Del Rio Oils Limited as Operator. Utilization was necessary to partially restorereservoir pressure by waterflooding. Studies indicated that waterflooding wouldincrease the recovery from 13.8 per cent to 31.7 per cent of the initialoil-in-place.