This paper describes the development and application of a laboratory procedure for the evaluation of screens for sand control. The driving force for this study was to provide an independent evaluation of all screens on the market, in particular, the new generation of premium screens. The test addresses both aspects of screen performance, namely sand retention efficiency and plugging potential. The difficulties in setting up such a test are discussed, with particular attention paid to the elimination of experimental artefacts. Some of the pitfalls that may be encountered in laboratory evaluation of screens are highlighted. The developed method has been used in screen selection tests for a particular field, and these results are also presented. The data illustrate the sensitivity of the technique for evaluating a range of screens on the same sand, and reasons for the differences in screen performance are explored. Furthermore, it was observed that the method of particle size analysis will affect the apparent particle size distribution of a sand. As a result such parameters as the uniformity coefficient may be completely different for the same sand depending on the method of size measurement.

fax 01-972-952-9435. AbstractEffective sand control and high well productivity throughout the life of the well have been defined as success criteria for the use of Stand Alone Screen as sand control strategy. This paper describes the strategy to meet these success criteria and illustrates the experience in Hydro Oil & Energy to date.A recommended practice for the selection of sand control has been established based on a comprehensive screen selection and fluid qualification process. The method includes testing and ranking of different screen designs based on sand retention and plugging properties for selected samples of reservoir sand. The screen design with the overall best performance is recommended for field application.In addition, requirements for drilling and completion fluids have been defined. Control of particle size and particle amount in the completion fluid has been identified as the most important criteria.Stand Alone Screen as sand control strategy have been successfully utilized for approximately 230 completions based on the presented methodology. For several of these wells, the established selection criteria published in the literature, recommended other sand control techniques to that used, e.g. open hole gravel pack. Based on Hydro Oil & Energy 's field experience the common practice for sand control selection applied within the industry today might be too cautious. It is concluded that Stand Alone Screen as completion method can have wider application than recognized so far.

There are two types of sand retention tests generally used in the industry to evaluate the performance of sand control screens for standalone screen applications: pre-pack tests and slurry tests. They represent complete hole collapse and gradual rock failure around the wellbore, respectively. In this paper, we present analytical results as well as Monte Carlo simulations to estimate sand production in slurry type sand retention tests with square mesh screens taking into account the full particle size distribution of the formation sand. We also compare the model results with experimental data and demonstrate that this approach can be used to predict sand production for different sand size distribution/screen size combinations without the need for physical tests. This work augments previously published slurry test models that were limited to wire-wrap screens, and enables comparison of the performance of square mesh screens to wire-wrap screens. The analytical model along with Monte Carlo simulations provide a direct and reliable way to estimate the amount of sand that will be produced for a given sand size distribution and a given screen size. Since the proposed methods are much more quantitative, they represent a significant improvement over current methods that rely on single design points or rules of thumb for screen selection.

In this paper we describe a simulation model for computing the formation damage imposed on the formation during over-balanced drilling. The main parts modelled are filter cake build-up under both static and dynamic conditions, fluid loss to the formation, transport of solids and polymers inside the formation including effects of pore lining retention and pore throat plugging, and salinity effects on fines stability and clay swelling. The developed model can handle multi-component water-based mud systems at both the core scale (linear model) and the field scale (2D radial model). Among the computed results are fluid-loss versus time, internal damage distribution and productivity calculations for both the entire well and individual sections. The simulation model works in part independent on fluid loss experiments, e.g., we do not use fluid leakoff coefficients, but instead we compute the filter cake buildup and its flow resistance from properties ascribed to the individual components in the mud. Some of these properties can be measured directly, such as particle size distribution of solids, effect of polymers on fluid viscosity and formation permeability and porosity. Other properties, which must be determined by tuning the results of the numerical model against fluid loss experiments, are still assumed to be rather case independent, and once determined they can be used in simulations at altered conditions as well as with different mud formulations. A detailed description of the filter cake model is given in the paper. We present simulations of several static and dynamic fluid loss experiments. The particle transport model is used to simulate a dilute particle injection experiment taken from the literature. Finally, we demonstrate the model's applicability at the field scale and present computational results from an actual well drilled in the North Sea. These results are analysed and it is concluded that the potential impact of the mechanistic modelling approach used is (a) increased understanding of damage mechanisms, (b) improved design of experiments used in the selection process and (c) better predictions at the well scale. This allows for a more efficient and more realistic pre-screening of drilling fluids than traditional core plug testing. Introduction A simulation tool, referred to as Maximize, has been developed for the purpose of investigating fluid loss to the formation during over-balanced drilling and the impairment imposed on the formation by the invading fluid. The objective of the program is to serve as a tool for supporting well planners' decisions related to the choice of well fluids, and integrating, analyzing and interpreting laboratory as well as field formation damage data. The filtration properties of the mudcake forming at the wellbore surface has been investigated by several authors over the years, see for example Ferguson and Klotz (1954); Outmans (1963), Bezemer and Havenaar (1966), Arthur and Peden (1988), Fordham et al. 1991 and Dewan and Chenevert (2001). The common understanding is that once the filter cake has been formed, it will control the filtration rate independent of the formation properties, except at very low permeability where the flow resistance offered by the formation is comparable to the filter cake resistance. The filter cake properties depend only on its composition, the pressure drop over the cake Dp and the shear stress acting on the cake surface by the circulating mud. Under dynamic conditions, the filtration rate will approach asymptotically a limiting steady-state rate which only depends on the shear stress at the cake's surface. A combined filter cake and simulation model was used by Semmelbeck et al. (1995) for computing the fluid invasion profile along the well. Further improvement of the filter cake model was presented by Dewan and Chenevert (2001), who demonstrated the derived model's capability to reproduce complex laboratory experiments with sequential changes in dynamic shear rate and overbalance pressure. Others, have also investigated filtrate invasion by numerical simulations e.g., Ding et al. (2002), Wu et al. (2004) and Suryanarayana et al. (2005).

fax 01-972-952-9435. AbstractEffective sand control and high well productivity throughout the life of the well have been defined as success criteria for the use of Stand Alone Screen as sand control strategy. This paper describes the strategy to meet these success criteria and illustrates the experience in Hydro Oil & Energy to date.A recommended practice for the selection of sand control has been established based on a comprehensive screen selection and fluid qualification process. The method includes testing and ranking of different screen designs based on sand retention and plugging properties for selected samples of reservoir sand. The screen design with the overall best performance is recommended for field application.In addition, requirements for drilling and completion fluids have been defined. Control of particle size and particle amount in the completion fluid has been identified as the most important criteria.Stand Alone Screen as sand control strategy have been successfully utilized for approximately 230 completions based on the presented methodology. For several of these wells, the established selection criteria published in the literature, recommended other sand control techniques to that used, e.g. open hole gravel pack. Based on Hydro Oil & Energy 's field experience the common practice for sand control selection applied within the industry today might be too cautious. It is concluded that Stand Alone Screen as completion method can have wider application than recognized so far.