Heterogeneities in the reservoir can result in poor sweep efficiency during water and chemical floods. In many cases the sweep efficiency is improved significantly when changing to polymer flood. However, in the presence of very high conductive features polymer by itself may not be sufficient and result in undesired polymer production. Diversion of the flow to oil saturated regions and minimization of polymer production is then desired. In the presence of cross-flow the best option is placing a (chemical) plug deep in the reservoir. Adding a second component to the injection polymer stream that can react with the polymer to form a cross-linked gel is then an effective solution. However controlled placement and triggering of the reaction is very challenging. In this paper we will present the results of static bulk measurements and dynamic core flooding experiments that were performed to identify cross-linked polymer systems. The polymers in the system are the typical high molecular weight partially hydrolyzed polyacrylamide (HPAM) polymers used in polymer flooding projects. The experimental work is focused on understanding and controlling the gelation time to enable proper placement and triggering at any given distance from the injectors. Parameters of investigation included temperature, brine composition, polymer concentration and rock mineralogy. The main parameters affecting the gelation process and possible failure mechanisms were identified. For given conditions, retardation of gelation time varying from few days up to several months could be designed. The learning from the experimental results can be used for improved material selection and design for other chemical and water flooding.

The volumetric sweep efficiency is an essential factor in the success of any water flooding or EOR project. Volumetric sweep efficiency (VSE) is controlled by the local reservoir geological settings, well patterns and completion design and production and injection strategies. In this paper we present a numerical modeling methodology to quantify VSE for different well patterns and geological settings independent of fluid types and saturation. The impact of conformance control techniques on VSE is estimated and the results translated to ultimate oil recovery for different driving mechanisms through standard analytical approximations. The methodology is used to evaluate the impact of conformance control techniques during water and polymer flooding for medium to high viscous oil reservoir. The results show that unselective blocking of high permeable layers during water flooding of high viscous oil reservoirs can be counterproductive and narrows the scope of potential chemical EOR opportunities. Polymer-(like) flooding wherever applicable is found to be in itself a very efficient conformance technique to increase the overall sweep efficiency for geological heterogeneities. In general abnormal high conductive features and long induced fractures tend to lower the efficiency of water or chemical flooding and cause excessive water/chemicals production to the surface facilities. Near wellbore mechanical treatments are then effective to minimize polymer production and increase oil production of which examples from ongoing polymer project will be discussed.

Well productivity is driven by establishing a clean connection through the near wellbore zone of drilling and completion induced permeability impairment commonly referred to as the "near wellbore damaged zone". This connection through the damaged zone is most often achieved by perforating with explosive shaped charges. The effectiveness of this connection is the result of perforator selection criteria and the well environment in which the perforating job is executed. In the depleted oil field under study a typical completion is perforated using large Tubing Conveyed (TCP) guns in "shoot and pull" mode in a static underbalance environment. After shooting the well is killed to allow the TCP guns to be pulled safely and the completion run. Production from the newly perforated intervals declines quickly due to near wellbore damage caused by the kill cycle. The challenge in this case was to identify the proper perforating gun system, conveyance method and perforating program to achieve the optimal productivity once the well is put on production. Modeling software was utilized to predict the productivity ratio (PR) for different perforating systems considering gun size, charge type, shot density, reservoir parameters and the well conditions at the time of shooting. The perforating program was modified to perforate the well with gas lift on in a flowing condition maintaining under balance conditions after shooting to assist with cleanup. The under balance at the time of shooting was managed using a permanent down hole gauge installed in the completion string. The first well completed using this process showed improved production of greater than 3 times what was expected when compared to similar wells in the field. This paper will cover the job design criteria, the job execution requirements and evaluation of the results. In addition, a summary of the study leading to this work and the total cost reduction details for the completion operations is also included. The result of this novel perforating job design has led to a new completion strategy for oil fields in Oman thus improving overall well performance. Introduction A key element of how productive a well will be is the effectiveness of the perforations. The perforation creates the path for the formation fluid to flow from reservoir to the wellbore. When the perforations are inadequate or plugged off inflow will suffer over the life of the well. The quality of the perforation job design and execution is a major concern in any completion design 1,2,3,4,5,6. An effective perforating job is dependent on many factors including:Perforating charge performance which is a function of reservoir rock strength, effective stress, fluid type and completion parametersPerforating gun characteristics such as gun size, shot density, phasing and charge typeWell conditions at the time of perforating including underbalance and fluid type in the wellboreWhat happens to the well post perforation e.g. a kill cycle which may damage the perforations and reduce productivity.

This paper discusses the use of downhole gauges not only for monitoring pressure and temperature, but also production-optimization, enhancing completion design, perforating activates and costmanagement efforts.Real-time downhole gauges have been used in oil fields for many applications in the past. Despite this, permanent downhole gauges have only been installed for gas-lift wells in one of PDO's fields since 2007. The requirement for the monitoring system was to closely monitor the bottomhole conditions for the purpose of water injection in a 5-spot pattern application.Openhole logs and individual reservoir pressure data of a well in 2007 indicated a variation in reservoir pressure values across the encountered zones. The decision to install permanent gauges offered the possibility to perforate the wells selectively in stages and measure the extent of underbalance prior to and during perforation operations. A technical and commercial comparison among perforation operations methods revealed that such an approach could result in better production performance and cost management. Data from the gauges provided ideas for improving perforation practices, such as spotting light oil against the perforated interval to minimize reservoir impairment.Installing permanent gauges in 2008 clarified three important areas: the wireline operations prior too perforation; the correct method for perforating; and the adherence to the issued program.While kicking off the well using gas lift, readings from the gauges revealed a gas-lift valve problem that instantly led to the decision to suspend perforation and change the malfunctioning valves. After rectifying the issue, perforating operations resumed and individual production tests were carried out to clarify the well's further potential. As a result, an operating-expense saving of more than $500,000 was achieved in the 2008 new well campaign. The added benefit of improved completion operations and production optimization has proved very useful.