ially hazardous, they must be planned carefully, both to keep wells

from getting out of control and to prevent or minimize the release of oil to the environment.

In response to the hazard of multiple

well involvement during workover accidents, the Geological Survey is currently revising OCS Order No. 8; this revision will limit the conditions under which multiple operations may be conducted on an

offshore structure.

The restrictions will apply to workover opera

tions as well as to drilling and production operations.

To increase production, acid or other fluid and suspended particulate matter may be pumped through the well bore into producing formations. The function of this treatment is to enlarge flow channels leading to the well. The spent acid returns up the well when production is resumed, and is handled as are other fluids from the well.

Sand produced along with the well fluids can cause the well periodically to plug, or "sand up", and must be removed. Other proce

dures to increase productivity and oil recovery include the injection of high-pressure steam, water and/or gas into specially prepared injection wells. The water used for this purpose may be taken from the ocean or from formation water. Water too contaminated to be

treated, polished, and discharged is reinjected into formations, taking suitable precautions to ensure that fresh water aquifers will not be contaminated by oil or salt water. Gas produced from the well may be reinjected for pressure maintenance where feasible or piped to shore for sale.

From the safety standpoint, completion and workover operations must be carefully conducted, and it is their critical nature that, in

all likelihood, makes these operations safer than they otherwise might be. Operators of swabbing and wire-line units are well aware

of the hazardous nature of their work and are extremely cautious.

Despite the potential hazard, safety records during wire-line and swabbing unit work are excellent.

e. Solid Waste and Sewage Disposal

Solid waste accumulating on offshore rigs consists

Solvents,

largely of common kitchen waste and shipping containers. additives, lubricants, and treatment chemicals are shipped in returnable drums.

All solid waste is collected in large containers constructed of heavy grating. To reduce the bulk before being transferred to shore, wastes are sometimes compacted in mechanical compactors but are generally incinerated in burn baskets suspended from the platform. Ashes are allowed to fall into the water.

Non-combustible

solids are then loaded into service boats for transfer to shore.

Solid wastes, transferred to shore, are emptied into municipal or private sanitary landfills which are subject to the sanitary landfill laws of the state.

Sewage treatment and disposal on offshore rigs and platforms is

very similar to the common septic tank, but with the addition of a chlorination system. In this case the septic tank is normally a

fiberglass container somewhere on the platform into which all toilet, kitchen, and laundry drains discharge. The usual settling and

bacterial digestion takes place in this tank and the final effluent

is chlorinated.

OCS Order No. 8 requires that the effluent shall contain 50 ppm or less of biochemical oxygen demand (BOD), 150 ppm or less of biochemical solids, and shall have a minimum chloride residual of 1.0 mg/liter after a minimum retention time of fifteen

minutes.

Nearly all hydrocarbons produced on the OCS are

transported by pipeline (as of 1971, only 31% of OCS crude oil was transported by barge). All natural gas, of course, must be moved by pipeline. A substantial amount of natural gas is necessary to justify economically the construction of a natural gas pipeline. In the early stages of the development of an oil field, small amounts of gas may be vented or flared or reinjected into the petroleum reservoir to maintain good pressure.

However, wasteful venting or

flaring is prohibited by OCS Order No. 11.

(1) Offshore

Pipelines laid offshore are constructed and

emplaced by several different methods, depending mainly on the size, location, intended use, and cost. One method, pipepulling, involves the use of barges and tugs to pull sections of welded pipe from an onshore launchway over the preselected right-of-way. These sections may either be dragged along the bottom or suspended by floats. are at least three limitations to this system. First, an extensive section of shoreline, roughly perpendicular to the shore, must be available for the fabrication and launchway site. (Alternatively,

There

it is possible although more costly to use a launching jetty con

structed from the beach out over the water.) Second, the total length

of pipeline that can be laid is limited. One company estimates the limit to be 100,000 feet for smaller diameter pipe. Third, the pipeline right-of-way must be essentially a straight line. The pipe pulling method is not used often for the emplacement of pipelines to OCS locations.

The second method, used in nearly all cases for large-diameter pipelines, involves the welding together of short sections of pipe on a barge while simultaneously moving the barge forward, and allowing the completed expanse of pipeline to sag downward and lay on the seafloor. This operation begins at the offshore location and proceeds toward the intended onshore terminus. The advantage of this system is that the pipeline right-of-way need not be straight, and that any diameter of pipeline can be laid in this way. The main disadvantage is the slow rate at which the laying proceeds; average rates are about 300-800 feet per hour.

The third method has become increasingly popular in the last decade for laying smaller-diameter pipelines and involves the use of a lay-barge equipped with a large reel or spool of coiled pipe. With the reel-pipelaying technique, miles of pipe are welded together onshore and the appropriate coatings are applied. Then the pipe is wound onto a large-diameter reel which is mounted on a barge or other floating vessel. The vessel is then transported to the construction site. As the barge is towed along the right-of-way,