Downhole gauges installed in Block 16/21 satellite wells have given invaluable real time data during extended well testing (Stirl ing and Blair) and have been extremely useful in gaining an understanding of Balmoral and Glamis well and reservoir behaviour in the early stages of production.The long term rel i abil ity of these systems has proved disappointing, highlighting the need for further eng i neering research and development in this area, particularly in sub-sea electrical connectors. It is hoped that experience gained with the reported systems will help others considering their use or those looking at further developments of downhole pressure systems.

Downhole gauges installed in Block 16/21 in the North Sea have given invaluable real-time data during extended well testing. These data have improved our understanding of Balmoral and Glamis well and reservoir behavior in the early stages ofproduction. The long-term reliability of these systems has been disappointing. We hope that experience gained with these systems will help others considering their use or contemplating further development of downhole pressure systems.

SPE Members Abstract Advances in computing technology have allowed the development of sophisticated 3D cellular modelling and visualisation software which has found a variety of applications in the oil industry. This includes spatial attribute modelling and the visualisation of hydrocarbon reservoirs to improve the understanding of the geological structure including internal features, the distribution of formation properties and the movement of fluids once field production begins. This paper discusses experiences gained in building a geological 3D model of the West Flank of the Alwyn North reservoir and the subsequent manipulation and transfer of this data into a 3D reservoir simulator for initialisation. The techniques used differ considerably from the traditional method using 2D surface mapping packages. The advantages of both geoscientist and reservoir engineer being able to see and review the 3D image of the reservoir at an early stage in the project is discussed. The paper covers the modelling of the reservoir's complex heterogeneities, the handling of both vertical and sloping fault surfaces, deviated wells and the contrasts in the number of cells of the geological model compared with the number of blocks in the reservoir simulation model. Procedures for up-scaling from geological to reservoir model are discussed along with the errors introduced in the transfer of data and subsequent re-sampling by different software packages. The paper concludes with suggestions for future developments of software to further enhance this effective method of modelling. Introduction The Alwyn North Field is jointly owned by Total Oil Marine plc. (operator), 33.33% and Elf Exploration U.K. plc., 66.66%. The field lies in blocks ½a and 3/9a of the Northern Sector of the North Sea, (Figure 1). The field produces hydrocarbons from both the Brent and Statfjord sandstone reservoirs. The initial recoverable reserves are estimated to be 218 MMstb of oil and 27 GSm3 of gas. The field came onstream in November 1987 and by the end of September 1993 had produced 170 MMstb of oil and 16.1 GSm3 of gas. The field can thus be regarded to be at a mature stage in its development. Extensive 3D seismic coverage has delineated a series of westerly dipping fault blocks which show extensive erosion and slumping along the eastern edge. There are two principle fault directions, a major NNW-SSE trend and a secondary ENE-WSW transverse trend. This faulting has divided the Brent reservoir into a series of five hydrocarbon bearing panels as indicated in Figure 2. The three panels comprising Brent North West, Brent Central West and Brent South West are referred to collectively as the West Flank. Four separate reservoir models have been constructed to cover the Alwyn North field. These are the Statfjord model, the Brent East model, the Brent North model and the West Flank model. It is the construction of the latter model which is discussed in this paper. P. 263^

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