Mitigating Water Injectivity Decline in Tight Carbonates due to Suspended Particles

Day 1 Mon, November 12, 2018

Shamouty

Tiwari

et al. 2018

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.

Successful Utilization of Extra-Long Lateral MRC Wells in Optimized Development of Tight and Thin Carbonates

Day 1 Mon, November 12, 2018

Shamouty

Tiwari

et al. 2018

Assessment of Fishbone Well Design Performance in a Tight Carbonate Compared to Single Extra-Long MRC Lateral

Day 3 Thu, September 19, 2019

Sowaidi

2019

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.

Assessment of Fishbone Well Design Performance in a Tight Carbonate Compared to Single Extra-Long MRC Lateral

Day 3 Wed, November 13, 2019

Sowaidi

2019

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.