Abstract

This case-history paper presents an account of the application of expandable (swelling) packers and a hydrajet perforating stimulation technique to perform a cementless completion and hydraulic stimulation in a 350o F, openhole horizontal well of 15,700 ft total vertical depth (TVD). Resulting production was more than three times that of an offset vertical well.

The first Wilcox Meek 2 well in the Brazos Bell Prospect Area was drilled and completed to test the effectiveness of horizontal well technology in tight-sand formations. This paper presents the cementless completion process and explores the effectiveness of horizontal-well technology in tight sands by comparing initial horizontal-well production rates to those of offset vertical wells.

The well, which was the first horizontal Wilcox in the area and probably the deepest horizontal well completion for a sandstone reservoir in South Texas, used a 5 ½-in. / 3 ½-in combination string as a production string. The 3 ½-in casing was run in the openhole horizontal lateral section and extended into the 7 5/8-in liner casing. It employed five swellable packers, strategically placed on the string to facilitate isolation for optimum stimulation results. An additional swellable packer, larger than the previous five, was run on the top of the 3 ½-in casing string and was placed inside the 7 5/8-in casing to help ensure complete isolation of the annulus. The swelling packers were activated over an 18-day period by hydrocarbons present in the oil-based mud (OBM) in the annulus.

Following packer activation, four fracture-stimulation operations were conducted in a non-cemented hole using a unique fracturing technique that incorporates hydrajet perforating with coiled tubing (CT). This technique allows for

  1. multiple stimulation treatments to be performed in series without the CT being removed from the hole,

  2. larger stimulation stages, and

  3. maximum surface-area exposure to the fracture pressure without formation damage caused by cement.

Introduction

The Wilcox formation is composed of gas-producing sandstone. High-temperature, high-pressure formations such as the Wilcox have reported temperatures of 350°F and above with typical geo-pressured conditions found below 12,000 ft in the onshore Texas Gulf Coast area. Zones of interest are located at ~15,500 to 15,700 ft TVD with porosities ranging from ~26 to 30%, and permeability of 0.001 md.

The purpose of drilling the Foster Farms Deep #1-H well was to test a 2,000-ft horizontal section of the Wilcox Meek 2 formation in the Brazos Belle prospect area of Southeast Texas. Vertical wells previously drilled in this area were successfully completed and fractured stimulated in the Meek 2. Over time, these wells have exhibited stabilized production of less than 1 MMcf/D of gas after initial flow rates that exceeded 3 MMcf/D.

While these wells are considered economical, a decision was made to use the latest technology in horizontal drilling and completion in an effort to enhance the productivity of Meek 2 wells drilled in the Brazos Belle area.

Drilling Operation

Since this was the first horizontal Wilcox well in the area and the deepest horizontal well drilled to the Wilcox in South Texas, the drilling program was modified to aid the successful drilling and completion of the 2,000 ft lateral section. The geometry of the borehole was designed to drill in the direction of the least horizontal stress to maximize wellbore stability, intercept most of the natural fractures (if any) in the reservoir, and obtain the best permeability of the producing formation while trying to minimize the tortuosity during the completion.

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