Pipeline pigs are devices that are placed inside the pipe and traverse the pipeline. Pigs may be used in hydrostatic testing and pipeline drying, internal cleaning, internal coating, liquid management, batching, and inspection. Figure 1 shows several types of pipeline pigs. Pigs are used during hydrostatic testing operations to allow the pipeline to be filled with water, or other test medium, without entrapping air. The pig is inserted ahead of the fill point, and water is pumped behind the pig to keep the pipe full of water and force air out ahead of the pig.
A typical tank battery contains two or more tanks and usually has a capacity equal to four days production. The suggested setting and connection plan for a typical tank battery is shown in Figs. 1 and 2. The pipeline connection in the tank should be located directly below the thief hatch and a minimum of 12 in. It should be equipped with a valve and sealing device immediately adjacent to the tank. Pipeline valves should be checked frequently for leaks. Drain connections should be located immediately above the tank bottom in the side of the tank or in the tank bottom immediately adjacent to the side.
Proper handling, both in transit and on site, are critical to avoiding damage to the tubing. This article provides an overview of inspection and handling considerations for tubing. API tubing is inspected at the mill in accordance with API Spec. Physical properties are checked and each length hydrostatically tested, normally to only 3,000 psi in the plain end (unthreaded) condition. Despite all the American Petroleum Institute (API) specifications and testing, some tubing defects are still found after delivery; thus, some operators do further inspection of new tubing on critical wells.
There are different definitions of what is Well Integrity. The most widely accepted definition is given by NORSOK D-010: "Application of technical, operational and organizational solutions to reduce risk of uncontrolled release of formation fluids throughout the life cycle of a well." Other accepted definition is given by ISO TS 16530-2 "Containment and the prevention of the escape of fluids (i.e. Well Integrity is a multidisciplinary approach. Well lifecycles have three primary areas of focus or stages; design and construction, well operation and intervention, and abandonment.
The American Petroleum Institute (API) developed Specifications, Recommended Practices, and Bulletins for steel tubing that meet the major needs of the oil and gas industry.API This effort continues, and many of these documents (with modifications) have become International Organization for Standardization (ISO) documents. Currently, API and ISO are the international standards for products intended for worldwide use in the petroleum and natural gas industry. The information in API and ISO documents is covered here in some detail. API tubing sizes range from ODs of 1.050 to 4.500 in. API and ISO specifications contain provisions when casing is used as tubing. In addition to API steel tubing, there are hostile well conditions that may be better served by other materials. There are proprietary steel grades that do not conform to all aspects of the API specifications but are used in the petroleum-producing industry for resistance to weight-loss corrosion, higher strengths, less susceptibility to sulfide stress corrosion cracking (SSC), and wear resistance. Corrosion-resistant alloy (CRA) is a special material that is sometimes used in hostile environments. These special materials are usually expensive but may prove worthwhile over the life of the well; however, CRA tubing does not always eliminate corrosion and may be incompatible with some completion fluids. Most thermoplastic tubing has good tension properties and burst resistance, but has relatively small collapse-pressure resistance and poorer wear resistance properties than steel tubing. If temperatures exceed 150 F, a derating service factor may be required. API has numerous manufacturing requirements for tubing. The tubing purchaser and designer should be aware of these requirements and of API testing procedures (see API Spec. In critical wells, the purchaser may want to receive and review the manufacturer' s test results. For tubing used in sour wells (wells with H2S content greater than 0.05 psi partial pressure), the specific sour service requirements should be reviewed.
Almost every vessel, barge, or floating object, including mobile offshore drilling units (MODUs), must have classification and registration certificates of compliance to the rules and regulations, as dictated and published by the classification society and country of registration. Most insurance underwriters require classification for the vessel to qualify for marine insurance. If the vessel is not fully classified, underwriting insurance companies will not insure the property, leaving the owner and his financial institution "self-insured." The vessel owner may consider the risk of a financial loss resulting from self-insurance, but his bank will not. Most operators will also require a drilling contractor to have classification on the MODU to show the unit's condition and seaworthiness.
Selecting the proper location for a storage tank is of prime importance. A typical tank battery contains two or more tanks and usually has a capacity equal to four days production. Tanks should be level with each other and have a minimum spacing of 3 ft between tanks, unless increased spacing is required by local code. Dikes are generally provided to contain the volume of a certain portion of the tanks enclosed depending on the tank contents. Dikes are used to protect surrounding property from tank spills or fires.
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. 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).
Remotely operated vehicles (ROVs) have facilitated the development of oil and gas resources in deeper water. By enabling access to areas that divers could not safely reach, they have extended capabilities for handling more complex situations and operations in deeper water. In the 1980s, divers used saturated and pressurized systems to do almost all well and subsea equipment intervention, inspection, and repair. If the divers could not complete the repair task and/or inspection, the blowout preventer (BOP) stack or other items had to be pulled out of the water for repair. Subsea television systems were, and still are, used to inspect and monitor hulls and subsea equipment by use of running down guidelines, but they can only view (not do) repairs or other physical tasks.