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An unconventional thin-bed analysis based on logs, core and miniperm data was needed to calculate the petrophysical properties of a reservoir under development in the Norwegian Sea. More than half of the reservoir section under investigation is composed of heterolithic facies: thinly interbedded sandstone and mudstone layers from one to several centimeters in thickness and of variable quality. By using miniperm measurements with 1-cm spacing on slabbed core, it was possible to resolve the properties of the rock far below the vertical resolution of conventional wireline logs and relate them to the bulk log measurements, P. 815

An unconventional thin-bed analysis based on logs, core, and miniperm data was needed to calculate the petrophysical properties of a reservoir under development in the Norwegian Sea. More than half of the reservoir section under investigation is composed of heterolithic facies: thinly interbedded sandstone and mudstone layers from one to several centimeters in thickness and of variable quality. By using miniperm measurements with 1-cm spacing on slabbed core, it was possible to resolve the properties of the rock far below the vertical resolution of conventional wireline logs and relate them to the bulk log measurements. Fig. 1-Core photographs showing sand-rich "light… and mudrich "dark… layers, interbedded at the centimeter scale, in a heterolith from the Heidrun Åre bayfill section. The left set was taken under white light; the right was taken under UV light.

SPE Members Abstract An engineering system has been developed for sand production prediction. The system synergistically uses geological reservoir characterization, log analysis, and core rock strength testing to forecast perforation cavity stability. Coupling the system with a reservoir simulator permits the modeling of cavity stability at initial conditions and throughout the life of a well. Three examples are given of applications of the engineering system to sand problems in North Sea reservoirs. Introduction Sand production prediction refers to the forecasting of perforation cavity stability in natural completions (i.e., perforated casing). When anticipated conditions of fluid flow or pressure drawdown lead to predictions of uncontrolled and potentially catastrophic sand production, alternatives to natural completions must be used (e.g., selective perforations, gravel packs). In many cases in mature producing areas, sand production prediction has come to be based on empirical relationships and historical precedent. In newer areas, especially offshore, completion engineers are challenged by the need to forecast sand production without analogous reservoir performance as a guide. The cost of positive sand control measures and deferred revenue from possibly reduced rates of initial hydrocarbon production provide the economic incentive for improved sand production prediction methodologies and optimized completion planning. For completion planning or analysis of sand problems of several North Sea reservoirs, an engineering system was developed to integrate geological description, log analysis, core testing, and reservoir simulation. This paper gives an overview of the generic engineering system that has evolved and of the types of data needed from exploration and development programs to make the best possible predictions of perforation cavity stability for completion planning. THE ENGINEERING SYSTEM Sand Production Causes and Constraints Sand problems can be induced by various causes and the consequences of sand production can affect various aspects of reservoir management. Because of the many factors affecting sand production, a strategy for optimized field operation requires comprehensive judgments integrating geology, rock mechanics, logging, production technology, and reservoir engineering. The engineering system starts by identifying constraints inherent in the reservoir or in production facilities. Constraints will help define an operator g ability to control sand production through reservoir management. Examples of constraints with possible impacts on sand production would include:High bubble point oil. To maintain high recovery from a high bubble point reservoir, the reservoir pressure and the well pressure should not be lowered below the bubble point.Erosional limits. Tubing and valves installed along the flow line may have erosional limits. To prevent excessive erosion, drawdown may have to be limited in such a well.Limited pressure support. Water injection rates may be limited in some reservoirs. P. 151^