Khazzan: Making the Most of the Fracturing Sweet-Spot Between Verticals and Horizontals

Abstract

Abstract Efficient hydraulic fracturing is one of the most important aspects for wells in tight-gas reservoirs, in order to achieve and sustain economic production. Unlike North America, where thousands of wells are drilled and completed each year and with infrastructure in place, delivering a tight gas field development (Khazzan) in the Sultanate of Oman has very specific challenges related to the limited number of wells and poor existing logistical infrastructure. In order to address these challenges, improve the frac process and overall development efficiency, a suite of high-level goals were set for the initial development, including zero accident(s), 1 Bcf/day production, 300 wells and 40 mm.scf/day IP per well. Within Block 61, in the Sultanate of Oman, the initial formation that was targeted for development was the Barik; a highly laminated gas bearing reservoir with measurable but tight permeability. The formation exhibits widespread heterogeneity in reservoir quality and rock properties in both the vertical and horizontal directions. Following an extensive exploration and appraisal programme, it was determined that vertical wells with massive hydraulic fracturing would be the most likely strategy for the higher permeability areas; with fractured horizontal wells being proposed within the lower permeability areas. This dual approach would provide the most efficient and effective development mechanism for the field and provide the greatest opportunity to deliver the simplistic development goals, as outlined above. During the exploration, appraisal and development phases of Khazzan, incremental learning and step by step improvement was required as the phases changed both the emphasis and requirements. This began with measuring resources, ensuring adequate service provision and logistics, completion set-up and subsequent transition from appraisal to development mode. The identification of key fracturing aspects, such as in-situ stress-state and geo-mechanical understanding, as well as frac geometry determination (both placed and effective) were crucial to achieving development progress. Post frac flow-back, initial production behaviour and reconciliation with petro-physics all played their part in the delivery of a rapid transition to efficiency along with proof of resource. This paper fully describes the technical and operational journey that was taken through the appraisal and early development phases, in order to fundamentally understand and deliver the most effective and efficient methods of hydraulic fracturing vertical wells in this tight-gas field. This case study includes the sequence of the first twelve vertical wells in the Barik reservoir; and the incremental improvements that were achieved in approaches over time. Fit for purpose technologies, equipment, procedures and surveillance have demonstrably led to a suite of very healthy and highly efficient completion approaches being adopted, which have ensured that the field development economics are being maximized.