Case History of the Development Drilling of the Southwest Sabine Tram and West Devil's Pocket Fields (includes associated papers 15986 and 15990)
- R.C. Penny Jr. (Arco Oil and Gas Co.) | A.W. Eustes III (Arco Oil and Gas Co.) | D.W. York (Arco Oil and Gas Co.)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- June 1986
- Document Type
- Journal Paper
- 177 - 182
- 1986. Society of Petroleum Engineers
- 5.6.4 Drillstem/Well Testing, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 5.5.2 Core Analysis, 2 Well Completion, 5.3.2 Multiphase Flow, 1.6 Drilling Operations, 4.3.1 Hydrates, 2.2.2 Perforating, 5.2.1 Phase Behavior and PVT Measurements, 2.4.3 Sand/Solids Control, 1.14 Casing and Cementing, 5.6.1 Open hole/cased hole log analysis, 1.11.4 Solids Control, 4.1.2 Separation and Treating, 4.1.5 Processing Equipment, 1.7.5 Well Control, 3 Production and Well Operations, 5.8.8 Gas-condensate reservoirs, 5.2 Reservoir Fluid Dynamics, 1.6.3 Drilling Optimisation, 1.11 Drilling Fluids and Materials, 1.5.4 Bit hydraulics, 5.1.2 Faults and Fracture Characterisation, 1.8 Formation Damage, 1.10 Drilling Equipment
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Summary. Drilling and evaluating the Wilcox formation have tong been challenging tasks. Lithology changes have made pore-pressure prediction difficult, while Wilcox water salinity and clays have made formation evaluation by openhole logging techniques virtually impossible. Optimization of very basic parameters-such as casing setting depths, mud properties, hydraulics, and evaluation techniques-have led to substantial reductions in time and, therefore, well cost. This paper outlines several improvements, learned from experience, that contributed to cost and time reductions in drilling and completing these Wilcox wells.
The West Devil's Pocket and Southwest Sabine Tram fields are located in southeast Texas about 22 miles [35 km] north of Orange, TX, and 3 miles[4.8 km] west of the Sabine River.
Since the discovery of these fields in July 1981, we have drilled 11 extension and development wells. The Upper Wilcox objectives are located between 11,500 and 11,800 ft [3500 and 3600 m] in five known productive sand intervals. The primary geological separation of the two fields is an east/west fault. The Upper Wilcox fields contain geopressured volatile oil and retrograde condensate reservoirs. Although the reservoirs are dissimilar, the drilling characteristics are nearly identical. Differences in drilling procedures for the two fields are noted. The wells are in three groups, representative of different phases of the learning and optimization process.
The first well studied was the Hankamer Section 1 Well 1, which was spudded on March 18, 1981, as an Upper Wilcox exploratory well. This well resulted in the discovery of the Southwest Sabine Tram field. The selection of casing points in planning this well was complicated by difficulties in estimating pore pressure in the Cook Mountain and Cane River formations. These formations occur from 9,700 ft [3000 m] to the top of the Wilcox at about 11,500 ft [3500 m]. A basic prerequisite for conventional pore-pressure prediction is the acquisition of good conductivity or sonic data in clean shales. Complications in plotting pore pressure were caused by the very silty nature of the Cook Mountain and Cane River formations. Problems in predicting pore pressure arose in the establishment of a nominal trend line because of a lithology change that occurred at the top of the transition zone. Sonic or conductivity departure curves can he established for an area on the basis of actual mud weights required to drill a particular formation. Before the area was drilled, a pore-pressure estimate was made on the basis of offset areas of similar lithology. Because the abnormally high-pressured Wilcox requires mud weights between 14 and 16 lbm/gal [1678 and 1917 kg/m3], it was necessary to set protective casing above the Wilcox and to obtain at least a 17.0-lbm/gal [2037-kg/m3] equivalent fracture gradient. To obtain such a high gradient at this depth, it was thought that pipe must be set in the abnormally pressured Cane River formation. Drilling to this depth required a mud weight of about 12.5 lbm/gal [1498 kg/m3]. To obtain the necessary fracture gradient to operate with 12.5-lbm/gal [1498-kg/m3]mud, the 10 3/4-in. [27.3-cm] surface casing was set at 4, 000 ft [1200 m]. This resulted in a 14-lbm/gal [1678-kg/m3] equivalent-mud-weight fracture gradient at the surface casing shoe. The 7 5/8-in. [19.4-cm] casing was set at 11,200 ft [3400 m], resulting in a fracture gradient of 17.3-lbm/gal[2073-kg/m 3] equivalent mud weight. The well was drilled to total depth(TD) (12,505 ft [3812 m]) in 66 days, which included a kick and lost circulation in the Wilcox. A 5 1/2-in. [14-cm] production liner was run and cemented at TD. Hole conditions-complicated by lost-circulation problems-resulted in a poor cement job. Production-zone isolation was attempted with numerous time-consuming and expensive block squeezes. Three Wilcox zones were tested while the well was evaluated. The tests were performed as cased-hole drillstem tests, requiring five completions to test the three zones. Conventional log analysis indicated that all three zones tested would be wet. Although two zones tested produced only water, the third was completed as a gas-condensate well with an 85 % water cut. The core data gave an optimistic evaluation of the third zone's productive potential.
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