TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFrac&pack has become a preferred completion method for the Duri field in Indonesia, where the reservoir is shallow, highly permeable and unconsolidated containing heavy viscous crude. This paper presents simulation of fluid leakoff and net pressure behavior for the frac&pack treatments in the Duri field. Several issues concerning selection of fracturing fluids and proppant, fracture dimensions and treatment designs are also discussed in the paper.A pressure-dependent leakoff model that is based on a transient flow of a polymer solution displacing a reservoir fluid is presented and coupled with a fracture mechanics model to investigate the interactions among the leakoff, net pressure and created fracture dimensions during different stages of frac&pack treatments. The results indicate that the leakoff is controlled by reservoir fluid viscosity and is dependent upon the rock-mechanics properties and the mobility ratio between the invaded solution and the reservoir fluid. In the absence of filtercake, the traditional leakoff notion using the concept of a constant leakoff coefficient fails to capture the transient behavior of polymer invasion and reservoir fluid compression. Because of high sensitivity to leakoff and the rock-mechanics properties, the net pressure behavior is also quite different from the one anticipated. For the typical formation with an elastic modulus of 50,000 to 100,000 psi in the Duri field, the net pressure is in a range of 20-40 psi during fracture propagation. The simulation also indicates that the net pressure over 200 psi would result in desirable fracture widths for Duri field applications.

TX 75083-3836, U.S.A., fax 01-972-952-9435. From the result above, CPI tried Frac and Pack (FP) completion. FP was first tried in Area 4-RVE Project. These wells were recompleted with FP completion into a shallower producing zone (Rindu Sand). Now, FP completion applies in almost all new and recompletion wells and has become the preferred completion method in sand control environments in DSF. wish to thank to CPI management for their permission to publish this paper.

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Summary This paper documents frac/pack completions conducted in the Duri field for the shallow, highly permeable, and unconsolidated formations containing heavy viscous crude. A treatment design model with a pressure-dependent leakoff option is presented to investigate effects of fracturing fluids, reservoir mobility, and Young's modulus on the fluid leakoff, net pressure, and fracture propagation. Field treatment data are analyzed with the provided model, and several factors that have significant influence on treatment results are discussed. Introduction Duri field is located in the eastern coastal plain of central Sumatra, approximately 70 miles northwest of the city of Pekanbaru. Oil is produced from a structurally trapped Miocene sandstone at depths between 200 and 900 ft. Duri field encompasses 30,000 acres and holds an estimated 5.4 billion bbl of original oil in place. It is the second largest oil field in Indonesia in terms of original oil in place. Rindu and Pertama/Kedua sands are two major producing intervals in the Duri reservoir where the combined pay thickness averages 250 ft and is located at depths between 250 and 700 ft. The formation has initial oil saturation of about 55%, average porosity of 34%, and air permeability in the pay formation ranging from 200 to 5,000 md. Currently, reservoir pore pressure is between 85 and 180 psi. The initial reservoir temperature is 92°F. The crude gravity is about 21°API (400 to 900 cp at the initial reservoir conditions). More information on typical reservoir properties is given in Table 1. In Duri, frac/pack became an attractive completion option owing to potential problems of formation damage and sand production. The first frac/pack pilot for the Duri field was conducted in 1996 for the Rindu Vertical Expansion Project.1 Some 500 wells of the Duri field were treated with cased-hole frac/pack techniques in 1999. Frac/pack techniques were widely implemented as a simultaneous solution for both sand control and production problems in highly permeable and unconsolidated formations.2–6 However, field experience indicates that some treatments do not perform as designed because of failure to achieve either tip screenout (TSO) or uncontrollable pressure growth. One of the challenges in treatment design and implementation is to accurately predict fluid leakoff in order to terminate fracture propagation at the desirable fracture length.7,8 However, prediction of the fluid leakoff is difficult because viscous fluids invade the formation and subsequently influence formation rock and fluid properties.9 Recent experiments also showed that spurt loss is a dominant leakoff phenomenon when the formation permeability is over 400 md.10,11 Therefore, the traditional model that does not account for spurt loss and fracture pressure is inadequate for modeling frac/pack applications in high-permeability formations.12–14 Recently, Fan and Economides introduced a leakoff model that predicts the transient flow of polymer solution displacing a reservoir fluid with a moving interface.15 The leakoff is pressure-dependent, with consideration of the pressure profile from the fracture face to the reservoir. In this paper, a frac/pack model with a pressure-dependent leakoff option is presented to study the interactions among the fluid leakoff, net pressure, and fracture dimensions for the Duri reservoir. The effects of fluid viscosity, reservoir mobility, and elastic modulus on the fluid efficiency and fracture net pressure are discussed. Field data are analyzed to demonstrate the model and its applications. Several aspects of treatment designs concerning selection of fracturing fluids, proppants, and treatment size are also discussed in this paper. Well-Completion Procedure in the Duri Field The bottomhole assembly for frac/pack treatment used in the Duri field is presented in Fig. 1. The completion event sequence is as follows.Rig-up and perforate intervals, with 180 phasing, 6 shots/ft, and 1.08-in.-diameter perforations.Wash perforations with KCl water between isolation cups.Run in hole with 6 5/8-in. wire wrap screen liner.Set modified fracture crossover with stinger.Perform minifracture on target intervals.Pump the frac/pack treatment per design.Pull fracture assembly out of hole.Set lead seal and place on production.

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