Experimental Study on Phase Characteristics of CO<sub>2</sub> Injection in BZ13-2 Strong Volatile Oil Reservoir in Bohai Sea Buried Hills
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Abstract:
BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO2 injection to improve oil recovery in near critical volatile oil reservoirs through CO2 injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO2 injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO2 injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery.Keywords:
Saturation (graph theory)
Miscibility
Gas oil ratio
Oil Production
Injection well
In this paper, the indexes have been determined for identifying ineffective injection production circulation and corresponding mathematical model was constructed with fuzzy theory. Application examples show that this method is simple, fast and accurate. For high and superhigh water cut oilfields, because of the long-term erosion of injected water, there are some high penetrative channels between the injection and production wells, resulting in most injected water along the channel to cause the invalid injection and production, for which it is hard to increase water flooding swept volume, causing flooding and high water cut well and reducing oil production. To improve the effectiveness of water injection to achieve stable yields, it is important to take the measures of ineffective injection-production wells profile control, plugging and so on for fast and accurate identifying ineffective injection-production wells. To that end, this paper applied fuzzy theory to establishing the mathematical model for identifying ineffective injection-production wells.
Water cut
Water flooding
Oil Production
Injection well
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Abstract The Guando field in Colombia, South America, is a sandstone reservoir with an initial pressure about 150 psi at GOC. A waterflood has been implemented since early in the life of the field. A complete set of data has been maintained on each of the injectors since 2002. This data set includes: daily injection rates, pressures, water quality and solids analysis. Injection into four different hydraulically fractured reservoir units is controlled by down-hole valves. In some cases wells are operated at injection pressures above the fracture gradient. To ensure good reservoir sweep efficiency, waterflood control and assurance of injectivity for each reservoir unit a detailed study of the injectivity of each injector was undertaken to understand the possible growth of fractures and its impact on frac-pack injectivity, injection profile and oil recovery. Field data indicates that the quality of river and produced water streams, mechanical configuration, stimulation of injector wells and injection facilities are important parameters that control the injectivity behavior. Injection well simulations are presented to show that the injectivity behavior can be history matched quite well and this process provides valuable insight into the dependence of injection parameters such as injection rate and water quality on injection profiles and fracture growth. This paper presents data and history match simulations for seven injectors from the field. The results allow us to estimate the fracture lengths that are created in the injectors and to thereby evaluate the effectiveness of injection schemes being implemented. This history match study allowed us to make recommendations for future injection rates and water quality into each of the injectors. To the best of our knowledge this is the first time that the injectivity of multi-layered, frac-packed injectors has been history matched with field data over an extended period of time. These history matched results validate our injection well model for frac-packed injectors and provide important guidance on future injection well design in addition to making concrete recommendations for the Guando field.
Injection well
Well stimulation
Reservoir Simulation
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The main problems existing in Mian-14 Area are imperfect injection-production pattern,serious oil reservoir heterogeneity and worse reservoir physical properties of Sha-4 Member.Recent years,through some rich remain oil zones had drilling new wells,increased water injection well spots and perfected injection-production network;on San-4Member conducted fracture reconstruction and boost pressure water injection;While on some water injection wells which with much interlayer differences conducted separate layer water injection,profile section adjustment and nitrogen injection.Based on a series of adjustment measures,some development effects had been improved to an extent.
Injection well
Oil Production
Water cut
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Abstract El Gassi is a volatile oil field located in the Algerian desert. The field has produced about 62 MMSTB oil since 1959, through primary depletion. Due to the heterogenity of producing formation, the total recovery during 45 years is only about 11%. The implementation of water-flood project was avoided due to low achievable water injection rate. A miscible gas injection project is examined in this study. The purpose of gas injection is to maintain reservoir pressure and improve the microscopic efficiency to increase the overall recovery in the field. A laboratory study revealed that the miscibility could be achieved with a pressure of about 241.4 bars (i.e. 3500 psia), which is below the reservoir average pressure in El Gassi field. Typical reservoir heterogeneities encountered in El Gassi field were incorporated into the simulation model. The study includes history matching of past reservoir performance, investigation of different injection scenarios, optimization of injection well number, optimization of gas injection and oil production rates, and the benefit of drilling infill wells. Edge line gas injection appeared to be promising.
Injection well
Infill
Reservoir Simulation
Oil in place
Secondary air injection
Workover
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Abstract The Bonga field has produced more than 275 MMstb in the last 4 years, a major contributor to deepwater oil produced offshore Nigeria to date. High production rates are being sustained as a result of the pressure maintenance scheme based on waterflooding that was implemented from the onset of production. Fully treated seawater is injected from 13 subsea high rate water injector wells daisy-chained on two separate water injection lines. To date more than 370 MMbbls of treated seawater has been injected in the field. High rates in water injector wells can only be achieved through fractured injection. Industry experience so far shows that matrix injection mode leads to declining well injectivity. However, for effective reservoir management, it is required that fractures created are not excessively large to cause integrity concerns on nearby seals, reservoirs and wells. Hence, it is necessary to predict the fracture dimensions for corresponding injection rates and pressures for effective waterflood management. The size (length and height) of an induced fracture depends on several parameters. This paper describes the use of an in-house fractured injection tool for estimating lateral and vertical extension of waterflood-induced fractures in Bonga wells. History matching of field data is performed to calibrate the model. Information from Pressure Transient Analysis and well interventions is used to improve model prediction. The analysis shows that with continuous high rate injection, long contained fractures are created in these high Darcy sands. Prediction results are used to define operating envelopes for these high rate water injector wells, with rates constrained in some wells to prevent induced fractures breaching the top shale layer.
Subsea
Injection well
Transient analysis
Well stimulation
Workover
North sea
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Abstract Waterflood injection on the Shell Bonga field offshore Nigeria is accomplished via a network of subsea flowlines and 15 subsea injection wells. Maximizing water injection volume is an important economic objective for Bonga. Water injection is used for maintaining the reservoir pressure and thereby maximize oil production. The water injection flowrate to each well is limited by the fracture pressure of the overlying shale layer. Fracture of overlying shale could significantly reduce oil recovery from the damaged reservoir. Hence, it is important to accurately control the reservoir injection pressure such that volume of injected water is maximized without excessive risk of damaging the overlying shales. Since there are no downhole pressure gauges in the injection wells, the downhole injection pressure must be estimated from other measured variables. For this, we developed a novel technology, WRIPS (Waterflood Reservoir Injection Pressure System). The WRIPS algorithm is used to: ■Estimate downhole injection pressure based on the model and available measurements■Estimate injection pressure uncertainty as a function of available measurements■Calculate an injection pressure target as a function of system conditions■Calculate injection rates for wells where the venturi has failed■Data reconciliation: calculate the most probable pressures and flowrates based on model, measurements, and sensor accuracies■Set conditioned alarm flags The paper gives a brief description and the experience gained with WRIPS applied to water injection wells. The main contribution from the paper is to demonstrate the benefits with such a system and that the WRIPS is an attractive solution compared to expensive downhole pressure gauges.
Subsea
Injection well
Pressure measurement
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One of the efforts that can be done to evaluate the performance of water injection in a field is by monitoring the injector wells. Observations can be made by looking at the flow rate and injection pressure at each injector well. The response given by each injection well will be able to represent the injection performance on a field scale. The EX structure is a structure that has been produced for more than 40 years. In addition, water injection has also been applied for approximately 16 years. There are four injection wells operating in this EX structure with an average injection flow rate of 3000-8000 bwipd per well. Evaluation of injection well performance is carried out by conducting a Hall Plot on each injection well from the start of the injection process to the last data obtained. Based on the evaluation results, it was found that there was plugging in the EA-IIS and EJ-IVS injection wells. Stimulation activity is needed in both wells to restore the well injection capability. Meanwhile, for the EA-IS and EB-IIL injection wells, there are no significant problems in those wells so they can still function properly as injection wells.
Injection well
Secondary air injection
Well stimulation
Injection site
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Abstract Peripheral water injection began into the pressure depleted Wafra Ratawi Oolite reservoir during July, 1998. Sixteen water injection wells are currently being utilized to inject 44,000 BWPD using low pressure charge pumps from the hydrocyclone and filtration skid. Design rate under high pressure injection is 200,000 BWPD using twenty-six injection wells. The water injection facility design, injector well location criteria, and reservoir performance data obtained from injectivity tests and spinner surveys are documented. Initial comparison between reservoir simulator predicted water injection rates versus actual injection rates provide some useful insight into the future success of the project. Recommendations regarding future operation of the injection facility and injection wells are highlighted.
Injection well
Water pressure
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In this paper, the indexes have been determined for identifying ineffective injection-production circulation and corresponding mathematical model was constructed with fuzzy theory. Application examples show that this method is simple, fast and accurate. For high and extra-high water cut oilfields, because of the long-term erosion of injected water, there are some high penetrative channels between the injection and production wells, resulting in most injected water along the channel to cause the invalid injection and production, for which it is hard to increase water flooding swept volume, causing flooding and high water cut well and reducing oil production. To improve the effectiveness of water injection to achieve stable yields, it is important to take the measures of ineffective injection-production wells profile control, plugging and so on for fast and accurate identifying ineffective injection-production wells. To that end, this paper applied fuzzy theory to establishing the mathematical model for identifying ineffective injection-production wells.
Water cut
Water flooding
Oil Production
Injection well
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Citations (1)
The stratified water is one of the main contents of the project to improve the recovery rate, to further improve the primary well pattern water flooding recovery, since 2010, Hu Jianshan oilfield continue to promote the fine layering water injection, separate water injection rate has increased substantially, with remarkable results. The process from 2009 to carry out the eccentric separate injection, 2011 promotion bridge eccentric separate injection, to2013 promotion bridge concentric filling, continuously expand the injection technology application in highly deviated wells, produced water reinjection wells, multilayer segmentation well, improve the injection well testing efficiency and accuracy, and gradually form the supporting technology of separate layer water injection technology of low permeability oilfield.
Injection well
Water flooding
Layering
Water cut
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