Abstract

The South Fuwaris field comprises of low to moderately permeable heterogeneous carbonate reservoirs, developed with horizontal bare-foot completions with increased pay-zone exposure. Hydraulic Fracturing conducted in tangent section of the production liner for a horizontal open-hole producer is shaping the development strategy for this field where conventional coiled-tubing matrix stimulations couldn't achieve the intended wormhole penetration due to inherent pumping rate limitations, and borehole enlargements had rendered Acid fracturing in open-hole only moderately successful. The inability to attain effective pressure containment necessary for formation breakdown had resulted in unsuccessful open-hole Acid fracture treatments in this field for both existing and newly drilled wells, either due to non-uniform bore-hole enlargement left-over by formation dissolution from previous matrix stimulations, or due to undulations and wash-outs in newly drilled laterals. To circumvent these operational limitations, the candidate well was drilled as a barefoot completion in the direction of minimum horizontal stress with an extended production liner to accommodate a cased-hole Acid Fracture treatment with transverse fracture orientation designed to drain a large section of the reservoir. Well testing was distributed into phases to interpret the production enhancement from this completion technique, to quantify contribution from the open-hole lateral after initial completion, from the isolated uppermost fractured interval immediately after the Acid Fracture treatment and the subsequent commingled production from both the open-hole lateral and the cased-hole fractured intervals. The key elements that led to the success of this project were the execution of well placement perpendicular to the fracture plane orientation as expected from local stress distribution, achieving an effective cement bond in the horizontal production liner and an advanced fiber based Acid-Fracturing stimulation designed to deliver deeper and infinitely conductive fractures. Evaluated in terms of operational cost savings and efficiency of the treatment execution, the treatment strategy is a major improvement over the conventional multi-stage assemblies previously employed for fracturing open-hole horizontal laterals in the South Fuwaris field. The job design eliminated the use of any complex permanent down-hole assembly for the fracturing treatment which means there isn't any reduction in the cross sectional area and hence no additional pressure drop imposed by flow restrictions and also a complete bore-hole access is available for future open-hole matrix stimulations or other interventions. The objective was to evaluate the existing completion strategy in South Fuwaris field for horizontal wells; to challenge the current ideology focused entirely on performance of long open-hole single or multilaterals, and focus more on reservoir development by way of fractures initiated entirely from the cased-hole horizontal section. The project's success has opened pathways to further explore in this direction to establish the optimum completion design for thin and tight heterogeneous carbonate formations like South Fuwaris.

You can access this article if you purchase or spend a download.