TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA review is presented on the state-of-the-art of mechanistic cuttings transport modeling. Cuttings transport predictions are essential for the planning of directional and horizontal drilling. It is suggested that field requirements (the need for fast, easy to use, simulators) point towards the use of a combination of two distinct modeling strategies, which are layer-models for the flow along the wellbore, and full numerical solutions in given cross-sectional areas. The layer model approach is developed in detail, yielding a two-layer model that simulates a moving bed of packed cuttings below a heterogeneous layer of mud and cuttings. Some key points on which more research is needed are highlighted.The model has been used to perform numerical simulations, predicting cuttings bed heights, pressure drops, and transport velocities at different rate of penetrations and mudflow rates. Results have been compared to predictions by correlation-based models. The observed differences are discussed and improvements on the current model are proposed.

This paper reviews the sand control practices used in an offshore Malaysia field, including execution of the longest single-trip multizone cased-hole gravel pack in Malaysia, the challenges faced, and the lessons learned. PETRONAS is currently developing an offshore field in Malaysia with wells designed to obtain medium-to-high production rates and be completed as gas-lifted dual-string producers. The lower sandface completion design was to gravel pack the lower and middle zones on a single run and selectively produce through the long string. The upper zone was then to be gravel packed and produce through the short string. Because of the long perforated intervals and exceptionally long distance between the producing zones, as well as different pressure profiles of the layers, shunt tube technique was identified as being the best practical method to overcome the operational challenges. The target reservoir is a laminated and multilayer sandstone formation. The lower and middle zones were gravel packed simultaneously with gross-producing intervals to 950 ft (the shaly section between the zones up to 600 ft). The upper zone was gravel packed separately with a gross perforated interval length to 775 ft. Due to the different pressures in the multiple zones, loss and crossflow control was a design requirement. The project imposed a number of challenges, including gravel packing extremely long intervals while aiming to achieve suitable perforation packing efficiency in unconsolidated and soft sandstone formations and also providing the possibility of selective production during the life of the wells. The proposed solution to overcome these concerns consisted of combining shunt tube technique with a three-way sub-concentric completion system. Five wells using this design have successfully been completed in this project with sand-free production rates exceeding expectations. The proposed solutions and the lessons learned in this project could change the sandface completion practices for multizone and long intervals in the offshore Malaysia fields. The techniques used in this project resulted in considerable rig-time savings, lower skin, and better productivity through improved perforation packing efficiency compare to the conventional methods.

A Brown field has been in production for over 30 years. A redevelopment plan started in 2004 to revamp oil production under an Alliance partnership between an Oil & Gas Company Malaysia and Schlumberger. The mentioned Brown field is a multilayered reservoir where the UCS can vary from 1500 psi in the consolidated sand until less than 800 psi in the shallow zones. Based on a geomechics study and existing production history of the field, unconsolidated producer sands were identified and sand control methods were evaluated according to the degree of achieving the goals, and reducing risk, the result indicates that the Cased Hole Gravel Pack with Alternate Path System was preferential. Additional information was obtained in the latest campaign during the retrieval of gravel pack screens in 2 sand producing wells, which gave a better understanding of the failure mechanism in the previous gravel pack operations. The main changes in the design of sand control systems during 8 years includes adopting a perforating strategy of performing a mechanical backsurge, increasing shot density and charges with low debris, use of a 3-way sub tailpipe system to avoid problems associated with breaking flapper valves and debris accumulation, number of cup packers, size of screens, slurry concentration and back pressure applied during the treatment. Furthermore the evolution in the sand control management have showed benefits such as increasing the number of gravel pack zones per well, performing longer gravel packs, installing permanent downhole gauges and using bigger tubing. This paper presents as case study of the evolution and the impact of the sand management systems, showing the significant changes in the design and execution of gravel packs and describing the reasons for those changes. The impact is analyzed on the basis of formation damage, GP factor, execution, risks and results of the initial production.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA review is presented on the state-of-the-art of mechanistic cuttings transport modeling. Cuttings transport predictions are essential for the planning of directional and horizontal drilling. It is suggested that field requirements (the need for fast, easy to use, simulators) point towards the use of a combination of two distinct modeling strategies, which are layer-models for the flow along the wellbore, and full numerical solutions in given cross-sectional areas. The layer model approach is developed in detail, yielding a two-layer model that simulates a moving bed of packed cuttings below a heterogeneous layer of mud and cuttings. Some key points on which more research is needed are highlighted.The model has been used to perform numerical simulations, predicting cuttings bed heights, pressure drops, and transport velocities at different rate of penetrations and mudflow rates. Results have been compared to predictions by correlation-based models. The observed differences are discussed and improvements on the current model are proposed.

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