AFE: support services
Drilling operations require the services of many support groups. Evaluating the types of support services that will be needed and estimating the cost of those services is an important component of well planning that must be reflected in the authority for expenditure (AFE) for the well.
Types of support service
Support service groups are used, because they can do a particular job more efficiently than the rig crew. An example of this efficiency is casing crews who are experienced in running large-diameter tubulars. Other support groups may provide services that cannot be performed by the rig crew or operator (i.e., well logging, pipe inspection, or specialized completions). Regardless of the reasons for using support services, their costs affect the total well cost and must be considered.
During the early years of the drilling industry, the rig crews ran all casing and tubing strings into the well. However, increasing well depths and tubular sizes made the process more difficult. In addition, items such as specialized couplings and pipe torque measurements gave rise to the requirements for the use of casing crews specialized in running the tubulars. Today’s industry uses not only casing crews but also groups specialized in picking up and laying down casing, tubing, and drillpipe.
Casing crew charges are dependent on crew size, pipe size, and well depth. Crew sizes usually range from 1 to 5 members. Fig. 1 shows the charges for a 5-member crew. In addition, a power-tong operator is required at rates ranging from U.S. $75 to $125/hour.
Monitoring services such as mud logging, cuttings interpretation, and gas monitoring are often used on deep or high-pressure wells. A variety of services at different costs are available. A few services and general cost ranges are shown in Table 1.
Formation-evaluation services, or well logging, are done on every well. The service may include formation evaluation, casing and cement logging, and hole-inclination surveys.
Charges for well logging vary with suppliers. However, some consistency does exist across the industry. Each logging operation will have a flat setup charge for each time the unit is rigged up (i.e., once for openhole logging call-out and once for cased-hole logging at each depth). A depth charge, usually on a per-foot basis, is applied to the deepest depth for each tool run. An operation charge is applied for each foot that the tool is operated. Estimation of the logging cost requires that a well logging program be established (Table 2). In addition, offshore logging is significantly more expensive than land operations.
Perforating charges may not apply, if the well is gravel packed or abandoned. The charges include setup, depth charge for minimum shots (usually 20), and a charge per shot over the minimum (Table 3). The total shots depend on the length of the productive zone and the shot density (e.g., 4 shots/ft). Assuming a setup charge of U.S. $750 and 20 shots as the minimum, Table 3 illustrates some of the costs involved with perforating.
Wireline formation testing is an economical method of obtaining reliable formation information. The repeating formation tester is a device that takes samples of pressure and fluids from a zone of interest. It should be included in the cost estimate for every exploratory well.
Charges for the service are on a depth and per-sample basis. Setup charges are usually not applicable, because the service is often run in conjunction with other logs. An example cost for a l5,000-ft sample would be U.S. $2,550/sample with a U.S. $0.55/ft depth charge.
Various types of production logs can be run on the well, if it is completed. These logs are generally run before perforation so that pre- and post-production formation evaluations can be made. Because production logging is a complex subject, the appropriate log suite must be developed jointly by the drilling and production engineers.
Pipe inspection is an important aspect of the casing and tubing program. These support services may include magnetic particle inspection, thread and end-area visual inspection, hydrostatic pressure testing, and pipe drifting. Typical charges for the services are U.S. $5 to $30/joint for each item and are service and pipe-size dependent.
Catering services for the galley of offshore or marsh rigs may not be included in the day-rate charges for the rig. The catering company will supply the cooks, support crews, and food for a per-man-day fee. Typical charges are U.S. $50/man-day for crews with less than 30 members and U.S. $47/man-day for crews with more than 30 members. For cost calculation purposes, average crew sizes for various rigs are:
- Marsh barge: 30 men
- Jackup: 50 men
- Floater: 70 men
Many items used on the rig and during drilling operations require specialized labor. These services are usually on a per-hour basis and at a minimum charge (4 to 8 hours). Typical considerations are:
- Welding :drive pipe, casing shoes, and general construction
- Rental equipment: equipment installation and repair
- Service representatives: packers, wellhead equipment, and chokes
In addition to the hourly charges for this labor, mileage and expenses must be considered.