document

Abstract

This paper describes an efficient multistage horizontal openhole completion technique as an alternative to conventional openhole or cemented and perforated lateral completions.  The application focuses on openhole (OH) completions in the Cleveland tight gas sand of the Texas panhandle. Horizontal wells have been drilled extensively in this low permeability gas reservoir to enhance productivity.⁽⁵⁾ While the increased contact area offers a potential for enhancing well productivity and overall well economics, additional stimulation is usually required. Conventional OH or cemented and perforated completion alternatives have had various operational and logistic issues that have minimized efficiency and production impact. The system applied involves the use of a series of mechanical openhole packers deployed on the production liner with a frac port located between each set of packers and a process of subsequent multistage stimulation of the entire interval.  The multistage OH completions have resulted in better connection to the reservoir compared to conventional cased-hole staged completions. Significantly increased completion efficiencies have been realized in all areas of the Cleveland tight gas sand, resulting in reduced completion costs and reduced overall completion timeframes.

Introduction

Geology, Completion Strategies

Cleveland Formation

The Cleveland formation was discovered in the mid-1950’s while exploring for the deeper Morrow reservoirs.  It can be found in Ochiltree and Lipscomb Counties in the North Eastern Texas panhandle as well as Ellis County in Western Oklahoma, covering an area of about 650 square miles with estimated total reserves of over 1TCFg(Figure 1).

The Cleveland is characterized as a fine-grained, tight-gas formation with clean sands often found to be interbedded with thin shale streaks at depths ranging from 6,500 to 8,500 ft TVD.  Permeability ranges between 0.03 md and 1.1md while porosity values lie between 4% and 14% (Table 1).

Initially, this area was developed through vertical wells drilled on 640 acre spacing. In a bid to effectively drain the reservoir, it was downspaced to 320 acre and more recently to 160 acres.  With the increase in gas prices, operators are constantly seeking ways to optimize the economics of wells in this area; maximizing the production potential of the well while minimizing completion costs. Horizontal wells have been drilled extensively in the Cleveland area as a result of this among other reasons, with a significant upward trend in horizontal versus vertical completions in the past four to five years (Figure 2).⁽¹⁾