This paper describes the simulation study done on optimizing the field development plans for undeveloped tight carbonate reservoirs with limited production history and surveillance data. The successful implementation of a water injectivity pilot test has enabled waterflood as a recovery method in the low permeability carbonate reservoir. The field optimization consists of three major components: well orientation, spacing and wellbore placement. Based on this study, a data collection program was proposed to target the uncertainties associated with developing the assets. The first part of the study focuses on the proper orientation of wells considering the factors of thermal fractures mitigation, developing the highest oil in place and ease of well drillability. The second part is concerned on studying the optimum spacing for achieving the target rate while maintaining an effective water displacement performance. The third part involved studying the well's placement for achieving a high rate early on during the production build-up while maximizing recovery in the long term. The combination of these three parts has led improved understanding of the important uncertainties associated with the reservoir which will be targeted in the ongoing appraisal program.

A reservoir simulation study of different fishbone well designs performance compared to a base development well design of extra-long maximum reservoir contact (MRC) single lateral wells is presented. The objective is to compare different well design concepts in a waterflood recovery scheme to achieve production target rate and maximize resource value for economic development of an undeveloped tight carbonate reservoir. The studied reservoir is located in a giant offshore oil field in the Middle East and was used as a representation of the different tight reservoirs within the field. It is characterized by poor quality rocks with a permeability trending from 2 – 0.5 md in a SE – NW direction. The study compromises an assessment of the achievable initial maximum oil rate, volumetric reservoir sweep and expected ultimate oil recovery factor for different well design concepts for a base short well spacing utilized for effective pressure support. In addition to that, the impact of fishbone well design on well count reduction potential utilizing twice the base short well spacing compared to single lateral wells development design utilizing the base short well spacing was evaluated. A sector model with equal producer to injector ratio was used with refined gridding to wells and bulk area gridded with a cell size of 10 m by 10 m in a representative area of the reservoir. The modeled wells incorporated with vertical flow performance tables with gas lift capabilities. The analysis also incorporated generating streamlines for analyzing fishbone well designs areal reservoir sweep and an examination of remaining movable oil areal distribution. An assessment matrix was formulated for comparing extra-long MRC single laterals base development design versus different fishbone well designs. The assessment matrix incorporated in addition to reservoir related flow performance indicators: drilling complexity and well cost, well life cycle activities, etc. for a comprehensive assessment. The main findings show that fishbone well designs have complicated areal sweep performance, especially with sealed motherbore, that result in a lower oil recovery factor with higher hydrocarbon pore volume injected and water oil ratio compared to extra-long MRC single laterals. Also, fishbone well designs have serious limitations during well life cycle activities compared to extra-long MRC single lateral design in terms of stimulation, well accessibility and well intervention options making the extra-long MRC single laterals the preferred field development concept within tight reservoirs especially with the base short well spacing. Finally, the analysis has shown that Fishbone well designs can't reduce the well count since base short well spacing is still needed for effective pressure support by water injection in addition to maximizing the oil recovery factor within the field life time and building and sustaining the target plateau.

This paper describes the field development planning strategy for appraising and developing an offshore reservoir area via extended reach extra-long maximum reservoir contact laterals drilled from an artificial island. These single production and injection laterals are completed in excess of 20,000 ft on top of tens of thousands feet of drilled well path to reach the drain landing point. These laterals have a dual purpose, as in addition to reservoir appraisal, is to maximize the productivity and injectivity in an on-going development of a tight carbonate reservoir. The well planning process starts from a careful selection of reservoir target coordinates to maximize the oil in place being developed from the artificial island and to enable reservoir testing and appraisal. From this data, initial 3D well designs are generated based on island location and rig capability to ensure ability to drill and run completion to total depth. The generated well tracks are used in a reservoir model to forecast production uplifts and inflow/outflow profiling along laterals. A strategic drilling step-out program has been implemented to extend drilling reach and completion deployment incrementally along with a reservoir surveillance program. The program was designed with built-in risk mitigations for any potential drilling and completion issues. The implemented program has enabled drilling into new areas and testing the reservoir properties at a small incremental cost of extending horizontal laterals. This has led to huge cost savings versus a very expensive appraisal program from a wellhead platform that included drilling a new well in addition to topside facility changes and pipelines conversions along with associated maintenance costs. The data gathered from these wells have enabled reduction of geologic uncertainty and de-risking of future developments. As a result, the field development footprint of developed oil resources was extended by additional 20% without the requirement of building additional drilling structures. Additionally, there is a well count reduction via lateral extension thus leading to capital costs saving. There were initial challenges encountered during lower completion deployment but they were resolved successfully in subsequent wells. An outcome of this strategy was the successful drilling of maximum reservoir contact wells with tens of thousands feet of drilled well path to reach the drain landing point and then with single horizontal drains exceeding 20,000 ft. The drilled wells resulted in unprecedented records in UAE and globally in terms of well total length, horizontal drain length and completion deployment.

This paper is about the study and utilization of Extra-Long lateral maximum reservoir contact (MRC) wells for development of the tightest and thinnest reservoirs in a giant offshore oil field in the Middle East. The objective is to derive production buildup towards company's target as economical optimized development plans are needed to maximize resource value. The key reservoirs for achieving the buildup target are characterized by poor quality rocks with permeability ranging from 3- to less than 1-md. Also, one reservoir is relatively very thin with 8 ft of payzone thickness where the oil resource density is low. Reservoir studies were conducted to overcome the challenges of developing these reservoirs that led to optimizing well spacing, orientation, horizontal lateral placement and maximizing lateral length to achieve objectives. For example, in tight reservoirs a 250 m well spacing was utilized for effective pressure support resulting in a high well density. MRC wells up to a maximum of 20,000 ft in lateral length are designed to maximize the productivity per well in low permeability formations while reducing the total well count resulting in reduced project capital expenditure (CAPEX) in terms of drilling and surface facilities costs by 20%. Extra-Long lateral wells also helped in reducing any potential anti-collision issues with current and future wells. The optimization of number and sequence of Extra-Long lateral MRC wells is expected to accelerate production build-up and minimize drilling costs taking into account the limited drilling rig availability. The development plans also accounted for implementing mitigations in addressing potential concerns encountered in the MRC wells life cycle from well construction process to production/injection phase. In the drilling and completion phase, new technologies were implemented for the first time and have resulted in a world record of completing the longest 6⅝in. cased lateral with a lateral length of 20,000 ft in one trip. These technologies have enabled accelerated delivery and lower construction costs for wells through application of a standardized well design process that helped in streamlining the drilling operations while reducing any potential risks. In the production and injection phase, all MRC wells are cased with 6⅝in. limited entry liners (LEL) to ensure full lateral accessibility for well intervention and retrofit operations. The specially designed liners ensure optimal stimulation along the lateral by providing mechanical diversion of the stimulation treatment delivered at high rate to provide more effective, cheaper and simpler stimulation operations. The utilization of sulphate reducing plant (SRP) for injection water with lower sulphate and particle content will reduce the number of stimulation and scale treatment jobs. Finally, all the preceding technologies and mitigations have led to successful implementation of the plan evidenced by production results that exceed production rate expectations from these challenging reservoirs.

A reservoir simulation study of different fishbone well designs performance compared to a base development well design of extra-long maximum reservoir contact (MRC) single lateral wells is presented. The objective is to compare different well design concepts in a waterflood recovery scheme to achieve production target rate and maximize resource value for economic development of an undeveloped tight carbonate reservoir. The studied reservoir is located in a giant offshore oil field in the Middle East and was used as a representation of the different tight reservoirs within the field. It is characterized by poor quality rocks with a permeability trending from 2 – 0.5 md in a SE – NW direction. The study compromises an assessment of the achievable initial maximum oil rate, volumetric reservoir sweep and expected ultimate oil recovery factor for different well design concepts for a base short well spacing utilized for effective pressure support. In addition to that, the impact of fishbone well design on well count reduction potential utilizing twice the base short well spacing compared to single lateral wells development design utilizing the base short well spacing was evaluated. A sector model with equal producer to injector ratio was used with refined gridding to wells and bulk area gridded with a cell size of 10 m by 10 m in a representative area of the reservoir. The modeled wells incorporated with vertical flow performance tables with gas lift capabilities. The analysis also incorporated generating streamlines for analyzing fishbone well designs areal reservoir sweep and an examination of remaining movable oil areal distribution. An assessment matrix was formulated for comparing extra-long MRC single laterals base development design versus different fishbone well designs. The assessment matrix incorporated in addition to reservoir related flow performance indicators: drilling complexity and well cost, well life cycle activities, etc. for a comprehensive assessment. The main findings show that fishbone well designs have complicated areal sweep performance, especially with sealed motherbore, that result in a lower oil recovery factor with higher hydrocarbon pore volume injected and water oil ratio compared to extra-long MRC single laterals. Also, fishbone well designs have serious limitations during well life cycle activities compared to extra-long MRC single lateral design in terms of stimulation, well accessibility and well intervention options making the extra-long MRC single laterals the preferred field development concept within tight reservoirs especially with the base short well spacing. Finally, the analysis has shown that Fishbone well designs can’t reduce the well count since base short well spacing is still needed for effective pressure support by water injection in addition to maximizing the oil recovery factor within the field life time and building and sustaining the target plateau.