State-of-the-Art Fracturing in the North Sea

Abstract

Introduction This paper will focus on recent advances in hydraulic fracturing technology with emphasis on North Sea applications. Five generalized applications that will benefit most from advances in technology have been identified. Because North Sea oil and gas field development requires the use of platform facilities for wellhead and processing equipment, deviated and horizontal wells are often used to effectively drain the reservoirs. Many of these wells require fracture stimulation. The success rate of such wells has increased significantly in recent years as a result of the following:Researchers better understand how fractures initiate and grow.Pre-treatment diagnostic techniques have improved substantially.Engineers better understand how completion design affects well performance. With improved understanding of post-frac well performance, engineers can evaluate the feasibility of developing a reservoir through fractured, horizontal wells. A significant number of the new fields developed in the North Sea will be marginal fields. As a result, the most advanced technologies must be used to ensure economic uccess, even though the funds available for pre-frac planning will be limited. Advances in diagnostic injection tests, real-time treatment analysis, and on-site redesign capabilities help ensure that hydraulic fracturing can be successfully applied in such marginal fields. Several high-pressure, high-temperature (HPHT) fields are currently being developed in the North Sea. Although HPHT fracturing has not yet been attempted in the North Sea, it has been successfully applied in other parts of the world. In addition to a review of the advances in HPHT technology that would apply to North Sea applications, this paper will identify improvements necessary before these techniques are applied in the North Sea. One of the most significant occurrences in fracture advancement is the expansion of fracturing techniques to reservoirs that traditionally were not considered fracturing candidates. Historically, hydraulic fracturing was considered an engineering tool for improving well productivity from tight, therwise non-commercial reservoirs. Now, however, hydraulic fracturing is being used more frequently (1) in high-permeability reservoirs to improve the overall profitability f the project, and (2) as an alternative to traditional sand control applications in soft, weakly consolidated reservoirs. The effect of hydraulic fracturing operations on the North Sea environment must be recognized. The advances in fluid design and post-treatment flowback procedures that minimize these effects are discussed. Fracturing Deviated and Horizontal Wells North Sea oil and gas field development requires the use of platform facilities for wellhead and processing equipment. Deviated and horizontal wells have a natural application in these conditions where wellheads are located close together yet reserves are located in a radial pattern around the installation. Many North Sea reservoirs require stimulation to maximize production rates and economic returns. As a result, propped hydraulic fracture treatments have been successfully used for both oil and gas production in horizontal and highly deviated wells in several sectors of the North Sea. In theDanish sector alone, over 300 propped hydraulic fracture stimulation treatments have been performed to date. The North Sea has led the industry in this technology.