Drilling Costs

Leases

The right to enter and drill on a property owner's land is accomplished by obtaining a lease. The lease is subject to title search and proper recording in much the same way as real estate.

Site Selection

In some areas, geology is a factor. For most developmental fields, road access to the site and nearness to gas pipelines are the most important considerations. Ability to reach the site in bad weather can affect income from the sale of oil and gas.

Permits

A survey showing the exact well site selected and an application must be made to the appropriate government agencies. After review, a permit will be issued stating requirements and restrictions, if any. At that point, the operator is free to drill.

Site Preparation

Most times, a road must be built to the site. At the site, a level area is cleared about 2/3 the size of a football field. A bulldozer is used for this job.

Drilling

When the site is prepared, the drilling rig can be moved into position. A rotary rig is the modern equipment used. It is capable of drilling over 1,000 feet per day through use of a rotating bit driven by huge engines. Fluid or air is forced under pressure down the center of the drill stem to clean out the hole continuously during drilling.

Surface Casing

To prevent possible contamination to drinking water and the surface, steel pipe of 8-5/8" is placed in the upper section of the hole. Cement is forced around this casing to form a solid bond between the pipe and the drilled hole. This pipe or casing may go as deep as 1,200 feet. After setting the surface casing, drilling is resumed with a smaller bit until the final desired well depth is reached.

Open Hole Logging

Special electrical and radio-active instruments are lowered into the completed hole. While being raised back to the surface, these delicate, sensitive instruments send signals to a computer on the surface. The computer converts the signals into a series of lines on a graph which, for comparison, might remind you of an electrocardiogram. The petroleum engineer with his specialized training can now determine the commercial probability of the well and where the best pay or production zones are located.

Production Casing

After the pay or production zones have been determined, the inside of the well is completed by lowering 4-1/2" steel pipe from the end of the surface casing to the bottom of the well. This pipe is then cemented in place in the same manner as the surface casing.

Closed Hole Logging

Additional sensitive instruments are now lowered into the hole to check that a good cement job was obtained and to further pinpoint production zones.

Perforation

To allow the gas and oil to enter the well, holes must now be made through the pipe and cement into the selected production zones. An explosive charge surrounded by 1/2" steel balls is lowered to the precise depth selected. Upon detonation, these balls are driven through the casing and cement is driven into the formation which contains gas and oil. This process is sometimes called a "perf" or "perfing".

Acidizing

An acid solution is put into the well to a level above the perforations. This will dissolve the surrounding cement and eat into the surrounding rock formation.

Fracturing

After the acid has done its job, an inert gas is forced into the well under very high pressure to fracture the rock formation containing oil and gas. This process creates fissures (cracks) through which the gas and oil can flow into the well. Sand is also forced into the well during this process and performs the job of bracing these fissures to keep the gas and oil flowing. The operator knows the fracture has occurred and been successful when the pressure suddenly drops on the gauges at the surface. The inert gas is then "blown off" at the surface until natural gas and/or oil begin to appear. Now, the underground process is completed.

Surface Completion

Valves and pipes on the top of the well (called a Christmas Tree) are then connected to a gas line through a meter where it goes to market. If the well also produces oil, then a pump, separator, and oil storage tanks will be erected to extract and store the oil. Trucks periodically enter the site to pick up oil and carry it to the purchasing refinery.