No abstract

Changing geological requirements during the development of a satellite field from the main Gullfaks platforms, resulted in the drilling of a "complex, mega reach, designer horizontal well". The original well plan, to reach a horizontal displacement of 4000m (13,123ft.) at a vertical depth of 2020m (6,627ft.), underwent significant modification as accumulating geological data was used to re-map the field. - Figure 6. We will demonstrate how pre-engineering studies, computer modelling and real time data recording allowed successful completion of the project and removed many of the perceived barriers to the development of out-lying structures.

The development of the Gullfaks field includes three giant gravity based platforms and subsea wells. This paper describes the field, the drilling program and the drilling equipment installed on the platforms. Shallow gas and abnormal pore pressure are among the challenges the operator faces. The block was awarded to a group comprising Statoil, the operator (85%), Norsk Hydro (9%) and Saga Petroleum (6%) in 1978. Exploration drilling commenced the same year. Introduction The Gullfaks field, located in block 34/10 in the Norwegian North Sea presents several challenges in well planning and drilling operations. (Fig. 1). These challenges include shallow gas, highly reactive clays, high pore pressures at relatively shallow depths and lost circulation problems. The first platform was placed in the field in 1986, the second one placed in 1987 and the third platform is scheduled for 1989. The platforms have 42, 42 and 52 well slots respectively. The concrete gravity base platforms have two drilling shafts and one drilling rig each. Five subsea wells are tied into the "A" platform. These subsea wells were predrilled and completed prior to final commissioning of the production systems oil the "A" platform. These completions were diverless and undertaken during the winter months. Special anchor patterns had to be designed and verified for each well owing to pipeline and control-line congestion in the area. Some 40 wells have been drilled to date in the greater Gullfaks area as exploration, appraisal, shallow gas, production and injection wells. one complicating factor is the presence of shallow gas in the area, which caused two incidents of gas flow. A special program to cope with the shallow gas was designed to eliminate potential hazards to the platforms. Field Development The field was declared commercial in 1980. The main concept for development consist of the following elements: (Fig. 2)–Three platforms of the Condeep type, two with four shafts, and one with three shafts. The drilling shafts are open to the seabed (wet). The "A" and "C" platforms are all-purpose with drilling, production and living facilities. The "B" -platform has limited process installations with only first stage separation and with the main power supplied from the "A" -platform. Phase i, in the fields total development plan, is to drill and produce reserves west of a main fault. The Gullfaks "A" and "B" platforms will be used to achieve this objective. Phase II will develop reserves east of the fault using the "C" platform.–Plans call for future subsea wells to be tied into all platforms to develop the reserves outside the drilling reach from the fixed installations. Five subsea wells are presently tied into the "A" -platform.–Offshore loading of oil is done via two buoys. Gas export is through the Statpipe gas system. P. 355^