Abstract

As shown by technical papers as early as the 1960s, our industry has long known that hydrajetting perforations or slots through cemented casing could often "bail-out" a problem well that otherwise seemed completely resistant to hydraulic fracturing attempts. For most of the first 50 years of fracturing applications, few operators had sufficient demand for the fracturing process to make it a commodity service, especially before the advent of coiled tubing (CT) services in the 1980s. Often, this type of well service was costly because of the need for both abrasive mixing and high-pressure pumping. In many cases, it was too time consuming to be practical as an "every-well" application, and lower-cost conventional explosive shape-charge perforating seemed sufficient for most wells.

As oil and gas prices have drastically increased in recent years, many operators have realized that for some well conditions, the use of hydrajet perforating (HP) can improve fracture stimulation efficiency and well economics. In a few cases HP has proven to be the only way that effective fracture stimulation could be achieved. In the past few years there has been a growing acceptance among both operators and service companies that hydrajet (abrasive jetting) perforating can improve overall well economics for fracture stimulated wells in many reservoirs. Some newer methodologies have combined hydrajet perforating and hydraulic fracturing into a single, continuous, multi-stage stimulation method. For many wells needing multiple fracture stimulations, significant reductions in nonproductive time (NPT) allows for reduced well costs even when more actual fracture stages are pumped. Use of more stages has often provided significant production gains and greater recoverable reserves.

Enhanced stimulation success in many moderately hard and very hard formations have proven the value of converting from shape charge perforating to hydrajetting as a stand-alone operation to avoid severe near-wellbore problems during hydraulic fracturing stimulation treatments. Since about 2000, and especially during the most recent 5 years, service providers have progressively expanded the processes, which included hydrajet perforating, especially in conjunction with hydraulic fracturing methods. This paper will review the expanding applications of hydrajet perforating in recent years, including case histories from several global applications.

Background

Early technical papers tell us that hydrojetting (w/o abrasives) was used with acidizing and fracture acidizing as early as 1939, primarily in zones completed open hole. However, with the incorporation of solid abrasives (hydrajetting, using abrasives) the jetting nozzles in use then could only perform for minutes before excessive erosion became a problem. The literature also reveals that around 1958 there was a renewed interest in sand-jetting and more abrasion-resistant carbide jets were developed. In May, 1961, the Journal of Petroleum Technology included three landmark publications that presented much of what had been happening since 1958 with respect to HP applications, and described other hydrajetting wellbore functions such as jetting cement from casing, cutting casing, scale removal, and other applications. The more extensive of these publications (Brown et al. 1961, and Pittman et al. 1961) had first been presented at technical conferences in October, 1960. The shorter, introductory article (Ousterhout 1961) indicated that by early in 1961 over 5,000 hydrajetting jobs had been performed with a success rate in excess of 90%; more than half of these were perforating applications. At that time, explosive/shape charge perforating was still in its infancy, with bullet perforating still common.

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