OTC PAPERS HIGHLIGHT OFFSHORE TECHNOLOGY ADVANCES

Here's a sampling of papers presented at the Offshore Technology Conference in Houston last week:

May 13, 1991

3 min read

Here's a sampling of papers presented at the Offshore Technology Conference in Houston last week:

The use of composite materials in offshore projects holds promise for cutting costs of deepwater field development, contends Conoco Inc.'s J.G. Williams. Applications under development include risers, tension leg platform (TLP) tethers, drill pipe, mooring lines, and high pressure tubing. Such material as graphite, Kevlar, and fiber glass can significantly reduce weight of offshore platforms, corrosion, fatigue, and maintenance costs. Williams estimates composites could cut displacement weight of a TP by 3 tons. But currently, composite use offshore is limited to such areas as grates and low pressure piping.
The industry may find 66203 small satellite oil fields in the northern and central North Sea, according to Brown & Root Vickers Ltd.'s G.P. Jenner and Heriot-Watt University's J.T. Ford and J.A. Tweedie. Of these fields, 60% may have reserves of 60 million bbl or less. The authors contend most North Sea fields with reserves of less than 100 million bbl are economically attractive for subsea tieback to existing production facilities. What's needed is development of technology to allow longer tiebacks. Currently, the longest tieback is 17 km, and about 50% of the prospective satellites are more than 15 km from a production facility. To correct this problem, the authors suggest subsea separation and multiphase pumps as a means for increasing the tieback distance.
Chevron U.K. Ltd.'s J.J. O'Conner, Goodfellow Lovie Associates Inc.'s P.M. Lovie, and Goodfellow Associates Ltd.'s M.M. Sarshar reported on status of a joint industry project for subsea separation. The last phase of the project, covering January 1989-May 1990, involved testing of a prototype in drydock. The authors conclude subsea separation is viable and cost effective for developing marginal fields and feasible with present technology. Subsea separation simplifies pumping requirements when existing pump technology is used. Such a system can be economically installed at distances greater than 18.6 miles from the mother platform. Even distances of 40-50 miles can be economic in certain cases, the authors contend.
Another type of subsea separation/pumping system is described by J.H. Entress and A.C. Baker of Baker, Jardine & Associates and D.L. Pridden of Mentor Engineering Consultants. This vertical annular separation and pumping system (Vasps) can be assembled from standard well and wellhead components. The concept involves installing a high capacity (30,000 b/d) separator and pump in the 30 in. conductor of a dummy well. The authors conclude the first stage, experimental and theoretical work, has demonstrated Vasps is effective. Stages 2 and 3 will involve prototype and field testing. A commercial system may be available in 1993.
Phillips Petroleum Co. Norway reported results of using a second generation intelligent inspection pig in the entire 714 mile Ekofisk pipeline system. Phillips notes pre-1987 intelligent pigs provided unreliable or inaccurate data. Although operating similarly to newer instruments, early systems' sensoring was much less sophisticated, and consequently accurate sizing of anomalies was impossible. Accuracy of the second generation intelligent pig was confirmed by field investigations of some of the report findings.
Conoco said a program to inspect and evaluate performance of subsea pipeline cathodic protection (CP) systems operated by Dubai Petroleum Co. (DPC) resulted in installation of 168 retrofit anodes in 7 years. The retrofit program will extend field life by 40 years. Involved were all 112 pipelines covering 277 miles in the two main fields, Fateh and Southwest Fateh, and two smaller fields, Falah and Rashid. Line sizes are 4-42 in. with most lines 12-18 in.