Largest Offshore Oil Research Articles

Noise control for offshore drilling facility

A detail noise survey was conducted on a large offshore oil rig with three drilling machines. The coherence function technique was used to identify noise sources in the equipment rooms, the control room, the radio room, the offices and the crew's living quarters. It was found that the major noise sources were diesel engine generators, mud pumps, air conditioners, ventilation systems, etc. The structure‐borne noises which were generated by engine generators and air conditioners propagated into the control room, the radio room, the offices and the living quarters through steel structures. Because this offshore facility will be operated in the North Sea, the noise levels should comply with the United Kingdom Department of Energy Guidance. Noise control recommendations were provided for the above mentioned areas and the work place on the drilling floor where the noise levels exceeded the criteria specified in the UK DOE's Guidance. The recommendation included the installation of vibration isolaters and silencers for the noise sources. These were successfully implemented. Acoustical treatments of a few special areas were suggested for further noise reduction.

Steep-fronted switching voltage transients and their distribution in motor windings. Part 1: System measurements of steep-fronted switching voltage transients

Insulation failure in motor windings can be caused by interturn breakdown resulting from stresses generated by steep-fronted transient voltages. The production and severity of such transients and degree of voltage stress on the motor-winding insulation is governed by the characteristics of the overall system to which the motor is connected. The investigations described in this paper cover extensive tests carried out at two large offshore oil production/water injection installations on a number of high-voltage motor circuits where motor failures had occurred. In particular, the tests were made to determine not only the nature and severity of the switching transients but also to determine the system characteristics governing their steepness and amplitude. For this purpose, the test programme included circuit-breaker timing tests, recurrent surge tests and synthetic tests in addition to full energisation tests. The results obtained and presented indicate that although, in all the circuits studied, steep-fronted transients are produced - in certain circuits, the amplitude of the transient would be sufficient to cause severe interturn insulation stresses in the motor winding. The system parameters that define the steepness of the transients and the combination of parameters that give rise to high-amplitude transients are evaluated. Tests with capacitors connected to the motor-winding terminals, to extend the wavefront duration of the transient voltages reaching the motor winding, are also described and discussed.

Studies of Offshore Reservoir With an Interfaced Reservoir/Piping Network Simulator

Summary A reservoir simulator and a piping network simulator have been interfaced to study reservoir deliverability. The interfaced programs are used for ongoing studies of several large reservoirs. An example of a recent study is presented to illustrate program usage. The interfaced system proves useful primarily for reservoirs producing through complex gathering systems. The system provides better forecasts of reservoir deliverability and is a useful tool in designing the gathering lines. Introduction A simulation model that combines both reservoir and surface facility calculations offers increased accuracy in predicting reservoir deliverability. This concept was presented by Dempsey et al. for a gas/water system. Simolte and Hearn described a recent application for study of a single-phase gas reservoir.This paper describes an interfaced reservoir/surface-facility simulation system used to study large offshore oil reservoirs that produced through complex gathering systems. A previous papers reported test cases run on an early version of the simulation program. The program subsequently has been refined to make practical and routine calculations for reservoir models with several thousand grid blocks and several hundred wells. Current usage is for ongoing design and deliverability studies of several major reservoirs.Fig. 1 shows an example of a hypothetical simulation model typical of recent application. The grid is a portion of the reservoir simulator grid. The platform locations and the surface piping network are superimposed. Several wells are connected to each platform.The formulations of reservoir and network simulators have been well documented in the literature and will not be described in detail in this paper. We will explain the following.1. The calculation procedure and approximations adopted to minimize central processing unit (CPU) time.2. Our technique for converging the reservoir and network simulator calculations.3. Applications of the system to example problems. Iterative Procedure A rigorous iterative procedure for the reservoir/network calculations was presented in Ref. 1 for gas deliverability calculations. Rigorous Iterative Solution For an accurate solution, the reservoir variables provided to the network simulator should represent the average or midtime-step values for the time step. To ensure that the correct values are used, it is necessary to iterate between the reservoir and network models within each time step.1. For each well, estimate average of midtime-step Pe, cut, and J based on initial conditions or extrapolation from previous time step.2. Solve network model given values from Step 1 to obtain individual-well flow rates. The step includes a calculation traverse for pressure drop from well bottom to network outlet several times until well rates converge. Step 2 represents a subiteration to develop well rates that satisfy the boundary conditions of Pe and fixed network-outlet pressure.3. Solve reservoir model for current time step using flow rates computed in Step 2 to obtain end of time-step pressures and saturations. Compute end of time step, cut, J, and P, for each well. JPT P. 399^

Petroleum Exploration and Production in Europe in 1972

Oil production from older producing basins onshore in western Europe continued to decline, but this was offset by increased production from the Ekofisk field in the Norwegian North Sea area, and from the first Danish offshore field to be commercially developed. Gas production in the British part of the southern North Sea increased to an annual average rate of 3.5 Bcf/d. In 1972 the most important exploration results continued to be in the North Sea basin. Large oil and gas discoveries were made in the British and Norwegian areas, and there were also favorable results from confirmation wells of 1971 discoveries and testing of wells suspended in 1971. New production licenses granted in the British offshore area in March included areas in the northern North Sea as well as we t of the Shetland Islands and in the Celtic Sea. Work obligations connected with these grants guaranteed a high level of exploration in the British North Sea area until at least 1978. Interest in European offshore prospects spread to the entire Atlantic shelf and to the Mediterranean Sea. The 1971 gas discovery south of Ireland proved of questionable commercial importance. The Amposta Marino oil field off eastern Spain was developed. Gas and condensate were found in a well in the Aegean Sea. In the Soviet Union production of oil was 7,813,000 b/d and of gas 21.3 Bcf/d, both showing a lower growth rate than in recent years. A large-diameter pipeline provided a new outlet to the southeast for the large oil fields of the middle Ob' Valley in the West Siberian basin, and the giant Medvezh'ye gas field of the northern West Siberian basin was put on production to a pipeline to Ural industrial centers. New oil fields were discovered in western Siberia, and gas was found in a previously nonproductive basin between the Aral Sea and Lake Balkhash. A second large offshore oil field was found in the eastern Caspian Sea. Large-scale gas production started in East Germany.