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Introduction

Habiburrohman abdullah

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Introduction

• Location to rig release.

• Wellbore diagram

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Location Rig to Release

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Overview

• The large investments required to drill for oil and gas are made primarily by oil companies.

• Small oil companies invest mostly in shallow, less expensive wells drilled on land.

• Investments in expensive offshore wells can be afforded only by large oil companies.

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Overview

• A well is classified as a wildcat well if its purpose is to discover a new petroleum reservoir.

• The development well is to exploit a known reservoir.

• Usually the geological group recommends wildcat well location, while the reservoir engineering group recommends development well location.

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Overview

• The drilling engineering groups make preliminary well designs & cost estimates for the proposed well.

• The legal group secures the necessary drilling and production rights.

• Surveyors establish & stake well location. • Usually the drilling is done by drilling contractor.

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Contracting the Well to be Drilled

• When a contract to drill an oil well is signed, many conditions and agreements are included. The drilling rig contractor will have agreed to drill a well to a specified depth. The conditions for payment are included. The contract payment may be based on the time on the location, a set sum of money, or by the foot.

• Most wells are contracted by the foot, but the contract is likely to make allowances for unforeseen problems and non drilling activities, such as time spent allowing the casing cement to set.

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Wellbore diagram

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Types of Casing

• Conductor Casing

• Surface Casing

• Intermediate Casing

• Production Casing

• Liners

• Tubing

Figure 1: Typical Well Diagram

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Conductor Casing

• A conductor string is a short length of large diameter pipe run where the ground is soft. It acts as a conduit to return drilling fluid to mud pits and prevents "cave in," the sloughing of ground around the rig base. It also protects shallow water sands.

• ODs: 16, 18-5/8, 20, 24, 30 and 36 inches.• Setting depths: 50 to 250 feet.

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Surface Casing

• Surface casing is the first string of casing used after the conductor pipe. It is required in some instances by law (to protect ground water) and is normally cemented full length.

• Surface casing supports the BOP stack and subsequent casing and tubing strings, and is normally the only string designed to carry compression loads.

• ODs: 13-3/8, 16, 18-5/8, 20, and 24 inches.• Setting depths: 200 to 5,000 feet.

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Intermediate Casing• Intermediate casing is any string between the surface and

production string. Intermediate casing may or may not be cemented full length.

• Intermediate casing may be used to seal off weaker zones from higher pressure drilling fluids required in subsequent drilling. It may also protect previous casing strings from higher burst pressures, and provide support for liner casing.

• ODs: 4-1/2 to 13-3/8 in.• Setting Depths: 2000 - 20,000 ft.

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Production Casing

• The production string is the primary pressure containment string It spans the total well depth and is not normally cemented full length.

• Allows segregation of producing formations and undesirable fluids from contaminating production equipment.

• ODs: 4-1/2, 5, 5-1/2, 7 and 7-5/8 in.• Setting Depths: 2000 - 30,000 ft.

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Liners• Liners are short casing strings run to isolate specific formations. As

they are normally short and relatively deep in the well, burst and collapse pressures control the design.

• Also, it is normal to have only one weight, grade and joint type in the string.

• Liners extend downward from the shoe of the previous casing string, and are normally cemented full length. Many liners use flush joint connections for improved clearances.

• ODs: 4-1/2 to 9-5/8 in.• Setting Depths: 5000 - 20,000 ft.

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Tubing• Tubing conveys the oil or gas to the surface. In some wells

dual or triple strings of tubing are used to isolate and produce different zones. In other circumstances, a dual string may be used where one produces and the other carries fluid pumped in to kill the well or to chemically inhibit the production string.

• Tubing is usually replaced on a regular basis because of the wear caused by producing fluids or gases.

• ODs: 1 to 4-1/2 in.• Setting Depths: 1000 - 25,000 ft.

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Casing Diagram

• MWD – after one stand drilled.

• EMS – taken every stand while POOH, crosschecking MWD survey.

• GSS – used when there is magnetic interference from casing string / fish.

• GMS – used when critical depth measurement is required for perforation, testing, etc.

Figure 2: Casing Diagram

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Example of Well Survey

Figure 3: Well Survey

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END