Some of the most challenging drilling encountered in the Uintab Basin of northeastern Utah occurs in the Altamont and Bluebell Fields (see Figure 4). Drilling costs in the area have been historically high due to such problems as surface water flows, lost circulation, abnormal pressure, hard and abrasive formations, and flows pressure, hard and abrasive formations, and flows of crude oil with high concentrations of paraffin.
Through implementation and improvement upon a carefully planned and executed drilling program, drilling costs in the area were reduced by program, drilling costs in the area were reduced by 48%. All wells used in this study were drilled using a fully company owned and operated drilling rig. This paper details the Improvements made in drilling fluids system, hydraulics, bit selection, solids control, cementing practices, and other drilling related parameters pertinent to our drilling success.
Introduction
The Altamont and Bluebell Fields, located in Duchesne County, Utah, went on production in 1971 and 1968, respectively. Production from the two fields amounts to 8400 BPD (1335 m3 PD) from 330 wells. Figure 1 shows a typical cross-section of the area along with the drilling and casing programs used. k 12-1/4" (31.1 cm) hole is programs used. k 12-1/4" (31.1 cm) hole is drilled to +/- 3000' (914 m) and 9-5/8" (24.4 cm) casing is set to isolate surface water flows and provide adequate kick tolerance. An 8-3/4" (22.2 provide adequate kick tolerance. An 8-3/4" (22.2 cm bit is used to drill out and 7" (17.8 cm) intermediate casing is set a 10,500 - 11,500' (3200 - 3500 m) to isolate weaker zones above and prepare for rapidly rising mud weights in the prepare for rapidly rising mud weights in the Wasatch formation. A 6" (15.2 cm) hole is drilled through the Wasatch and a 5" (12.7 cm) production liner is set. production liner is set. Since commencing the second well on a lease development drilling program in November 1983, eight wells have been drilled and completed in the Altamont/Bluebell Fields (see Table 1). The Dillman 2-28A2 was the first well drilled by the Casper Division in the Bluebell Field since 1975, and was drilled using accepted Altamont/Bluebell drilling practices and technology. The well was drilled to a TD of 14,400' (4389 m) in 95 days at a drill and complete cost of $3.019MM or $209.65/ft (see Figure 2). It was immediately recognized that the development project economics would not support well costs of this magnitude. Due to the rapid draw down of wells in this area, low initial well cost is essential if the wells are to pay out in a reasonable amount of time.
A total review of Altamont/Bluebell Fields drilling and completion practices was made with emphasis on reducing the total well cost. Based on available bit records, the average drilling time for a Wasatch well in the Altamont/Bluebell Fields was 60 days prior to February, 1984.
