Openhole Expandable-Sand-Screen Completions in Brunei
- Hon Chung Lau (Brunei Shell Petroleum) | Jacques van Vliet (Brunei Shell Petroleum) | Mike Ward (Brunei Shell Petroleum) | David Morin (Brunei Shell Petroleum) | Arifun Djamil (Brunei Shell Petroleum) | Paul Kuhnert (Brunei Shell Petroleum) | Walter Aldaz (Weatherford Completions Systems) | Steven Shanks (Weatherford Completions Systems)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- March 2004
- Document Type
- Journal Paper
- 46 - 51
- 2004. Society of Petroleum Engineers
- 3.2.5 Produced Sand / Solids Management and Control, 2 Well Completion, 4.5 Offshore Facilities and Subsea Systems, 4.1.2 Separation and Treating, 4.1.5 Processing Equipment, 3.3.6 Integrated Modeling, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.6 Drilling Operations, 1.11 Drilling Fluids and Materials, 1.2.3 Rock properties, 5.1.5 Geologic Modeling, 2.4.3 Sand/Solids Control, 5.5.2 Core Analysis, 2.4.5 Gravel pack design & evaluation, 2.3 Completion Monitoring Systems/Intelligent Wells, 1.10 Drilling Equipment
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Expandable sand screens were deployed successfully as a sand-control device in two horizontal openhole completions in two geologically different offshore fields in Brunei. A critical success factor was the choice of a drill-in fluid (DIF) that maintained hole stability and gave a near-gauge hole while running and expanding the sand screen. Field experience and extensive research led to the choice of a synthetic-based DIF for one well but a water-based one for the other. Challenges unique to the deployment of expandable sand screens in these wells are discussed.
The expandable sand screen is an innovative technology that is gaining wide acceptance in the industry as a simple and reliable sand-control technique.1,2 The slim nature of the design facilitates screen deployment in various openhole applications, including high dogleg severity and horizontal wells. After deployment, the screen is expanded to eliminate the annulus, making gravel-packing operations unnecessary in reservoirs that carry risks, such as reactive shale, low fracture gradient, fractures, or faults.
An expandable sand screen consists of multiple overlapping rectangular sheets of metal-weave filters attached to an expandable base pipe and encased within a protective metal shroud (see Fig. 1). It can be expanded by a solid expansion cone followed by a compliant expansion tool. During expansion, the base pipe and the protective shroud's slots open to expose a flow area through the metal-weave filters, which accommodate the expansion by sliding away from each other while maintaining a tight overlap at all times. The effective filter aperture remains constant and unaffected by the expansion process.
The expandable sand screen has a number of unique advantages. First, it offers a large inflow area that minimizes screen plugging and erosion. Second, it is operationally simple to install. Third, it offers a larger internal diameter than most sand-control screens, thus facilitating tubular installation for zonal isolation. Fourth, in openhole applications, an expandable sand screen elimi- nates the annulus between the screen and the sandface. Therefore, it stabilizes the sandface and minimizes sand movement, thus reducing the risk of sand failure and screen erosion caused by sand production.
To date, Brunei Shell has completed several cased-hole3 and openhole oil and gas wells with an expandable sand screen as the sand-control device. This paper discusses the first two applications in long openhole completions in two different offshore fields in Brunei. The first application was in the Champion field, and the second was in the southwest Ampa field. These wells are discussed in reverse order here.
Expandable-Sand-Screen Application in the Southwest Ampa Field
The southwest Ampa field consists of many thin, stacked sand layers separated by shale stringers. Many wells in this field have a history of sand production, making sand control a necessity. Sand control in openhole completions transecting multiple sand layers is particularly challenging because of shale-stability issues. This field had a history of unsuccessful openhole gravel packs thought to be associated with shale collapse once the openhole was displaced to brine. Caliper logs showed that with increasing openhole time, the shale sections tended to be overgauge, while tight spots developed in the sand sections. Following several unsuccessful openhole gravel packs, extensive laboratory research was conducted by the operator's technology and application group in Houston to determine if expandable sand screens could be used as an alternative sand-control method. The following sections discuss the major findings of this research.
Mud/Shale Interaction Test Results.
Samples of shale cored from several wells were analyzed in the laboratory. X-ray diffraction data showed a complete absence of smectites and an abundance of illites, kaolinites, and chlorites in the clay components. The mud/shale interaction tests conducted included a capillary suction test, linear swell meter test, cuttings dispersion, pore-pressure penetration tests, and visual stability observations of shale in contact with various brines, water-based polymer, and ester-based DIF.
Visual observations at room temperature and pressure showed that Ampa shales disperse quickly in KCl and CaCl2 brine, slowly in water-based DIFs, and not at all in an ester-based DIF. Pore-pressure-transmission tests conducted on Pierre shale showed that both CaCl2 brine and water-based DIFs have almost no resistance to pore-pressure penetration. However, an ester-based DIF reduces the effective shale permeability by two orders of magnitude - from 33 to 0.37 nD - and gives the greatest resistance to pore-pressure transmission. These tests showed that the brine in water-based DIFs invades the shale, causing pore-pressure equilibration and leading to shale failure with time. The driving forces for filtrate invasion are hydraulic overbalance and osmotic-driven diffusion. On the other hand, an ester-based DIF shows almost no pore-pressure penetration because of the high capillary entry pressure of the oil phase; hence, the shale is stable.
The mud weight required for mechanical stability of the shale during drilling was calculated using the operator's proprietary wellbore-stability model. Specific well input, such as true vertical depth (TVD), inclination, pore pressure, minimum and maximum horizontal stresses, vertical stress, Young's modulus, Poisson ratio, and formation-specific data, such as the friction angle and cohesion extracted from shale samples, was used in the calculations. The model showed that a mud weight equal to the pore pressure plus a trip margin is not enough to stabilize the hole when drilling weak formations, such as shales at high deviation. This is because in a deviated hole, the wellbore starts to carry part of the vertical stress. Therefore, in a weak formation like shales, a higher mud weight is needed to stabilize the wellbore.
Experiments were conducted to determine whether an ester-based DIF plugged an expandable sand screen during run-in and expansion. Results showed that an unconditioned DIF has a high tendency to plug an expandable sand screen whereas a DIF that has gone through an appropriately sized shaker screen has the least tendency to plug the sand screen.
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