Abstract

This case history paper presents fracture stimulation using coiled tubing (CT) hydrajetting, followed by (1) annular-path pumping of the fracturing treatment and (2) use of high-concentration proppant slugs to create proppant plugs for diversion. The process of hydrajet perforating and annular-path pumping (HPAP) has been used effectively for vertical well completions and is especially applicable for multi-interval completions. Further, use of this process for multi-interval fracturing of horizontal well completions has been performed successfully in several North America reservoirs, and in Texas at depths below 15,700 ft true vertical depth (TVD) and measured depths (MD) of more than 16,700 ft.

Cased and cemented horizontal completions present several challenges for the HPAP method, including (1) unique CT calculations and operating procedures, and (2) proppant plug-setting procedures. This multi-stage completion process can also be applied in other methods of horizontal completions that incorporate a solid liner.

Several case histories are examined to (1) highlight lessons learned in performance of this method on horizontal well completions, and (2) demonstrate efficiencies gained as compared to following conventional practices.

Introduction

Fracturing methods aimed at improving operational efficiency by reducing nonproductive time (NPT) have increased in importance as assets are being completed that involve multiple intervals, thick pay intervals, or horizontal wellbores (McDaniel 2005). Some of these methods, such as the use of high fracturing rates and limited-entry perforating, greatly reduce the overall completion time but have been shown to be less than adequate in stimulating all targeted intervals (Craig et al. 2005).

Other fracturing methods that focus on treating intervals individually can result in many hours of NPT mainly as a result of discrete process steps that require trips in and out of the well between treatments while pumping equipment resources remain idle or are required to leave and return to the wellsite. These discrete steps include trips for (1) perforating, (2) setting or moving tools such as bridge plugs, and (3) wellbore cleanouts.

In the late 1990s, a hydrajetting process (Surjaatmadja 1998) called hydrajet-assisted fracturing (HJAF), using dynamic diversion, was introduced to the industry as a means of treating horizontal wells, in particular openhole horizontal completions (Surjaatmadja et al. 1998; Love et al. 1998; McDaniel et al. 2002). The benefits of this process for reducing NPT were readily apparent and horizontal completions involving 20 separate fracture treatments in a single well have been performed in just 2 days of daylight operation (East et al. 2004). The process uses hydrajet perforating and HJAF, which eliminates a separate trip into and out of the wellbore (Fig. 1). The numerous advantages (and some limitations) of using hydrajetted perforations instead of explosive/shape charge perforating has been recently reviewed extensively in a recent paper (McDaniel et al. 2008).

Because the HJAF process relies on dynamic diversion, no mechanical plugs are required to furnish diversion between intervals being treated. Therefore, there is no drilling of plugs or plug-retrieval operations after the treatments have been performed, further reducing NPT in the completion process. The HJAF method allows for recovery from premature screenouts because tubulars are in position for rapid cleanout of excess proppant at each stage of the fracturing and perforating process. This is particularly beneficial when aggressive proppant schedules are required, such as in the case of frac-pack or tip-screenout treatment designs.

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