Eliminating Multiple Interventions Using a Single Rig-Up Coiled-Tubing Solution
- Kumar Santhana (Petroleum Development Oman) | Stan J. Van Gisbergen (Petroleum Development Oman) | Jeremy Harris (Petroleum Development Oman) | Erik Ferdiansyah (Petroleum Development Oman) | Mark E. Brady (Qatar Shell GTL) | Salah Al-Harthy (Schlumberger) | Arum Pandey (Schlumberger Oilfield Services)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- May 2008
- Document Type
- Journal Paper
- 119 - 124
- 2008. Society of Petroleum Engineers
- 5.8.7 Carbonate Reservoir, 3.1.2 Electric Submersible Pumps, 5.4.1 Waterflooding, 4.1.5 Processing Equipment, 3.2.2 Downhole intervention and remediation (including wireline and coiled tubing), 5.1.2 Faults and Fracture Characterisation, 1.10 Drilling Equipment, 3 Production and Well Operations, 3.1.6 Gas Lift, 1.6 Drilling Operations, 1.14 Casing and Cementing, 2.2.2 Perforating, 4.3.4 Scale, 2.4.3 Sand/Solids Control, 1.7 Pressure Management
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This paper describes new methods to economically improve production levels in one of the mature fields of Petroleum Development Oman. This field had been developed by infill drilling programs, which were suspended in early 2001 to review the development strategy. A reservoir management team set a challenge to effectively conduct logging operations and quickly use the data collected to identify and avail of optimization opportunities. The ensuing campaign resulted in maximizing the production of the wells whilst lowering overall costs. The optimization activity consisted of clean-out, saturation logging, perforation, and stimulation. These activities were initially carried out in two ways: 1) with coiled tubing using only conventional coiled tubing and e-line coiled tubing or 2) with the combination of coiled tubing and a hoist. Both methods involved multiple well entries. Both of these methods were successful in that they resulted in incremental net oil production but at relatively high costs.
This paper presents an enhanced methodology which enables clean-out, logging, stimulation, and perforation with one coiled- tubing intervention, which includes a plastic-coated "e-line?? coiled tubing, coiled-tubing perforating head, and new perforation technology. All systems are in complete compliance with the most stringent safety criteria. The new method has a considerable time and cost savings impact. These results are fully illustrated in this paper with field trial case histories, in which a multi-disciplinary team effectively targeted the most suitable zones for perforation and stimulation by use of a state of the art self-diverting, non-damaging, acid system. Technical and economic comparisons are made with conventional practices. The new methodology is currently being used in this field and is potentially applicable to other fields.
The field under study is in north Oman and has been operating under waterflood conditions since 1972. The reservoir is positioned within the Lower Cretaceous Shuaiba formation, which is a chalky intrashelf basin floor carbonate mudstone. Porosity ranges from 30 to 35%, while permeability ranges from one md at the base of the Shuaiba to 200 md in thief zones at the top. Average matrix permeability is approximately 10 md. Permeabilities in fault and fracture zones are believed to be orders of magnitude higher than the average matrix permeability. Most of the production comes from horizontal wells with a perforated 4 ½ in. cemented liner. The average water cut from this field is currently 93%. The high water cut presents longer term concerns, and Petroleum Development Oman has implemented a multi-disciplinary effort with the ultimate goal of improving production through sound reservoir management practice together with concerted coiled tubing (CT) and workover-rig (hoist) intervention operations. A thorough evaluation of candidate selection is conducted by use of appropriate reservoir evaluation techniques with strong consideration to geology.
The development activities in this field traditionally had been targeted by infill drilling with vertical wells until 1994, followed by horizontal wells. The infill drilling targeting attic oil was suspended in early 2001. An integrated field review was started to design the next stage of field development to maximize the remaining value through effective well and reservoir management. The reservoir management team identified the need for data gathering including the monitoring of reservoir saturation by running pulsed-neutron-capture tools (PNC) to identify additional perforation opportunities. In gas-lifted wells, the PNC logging was run on coiled tubing and in wells with Electrical Submersible Pumps (ESP) by pumping down the PNC tool inside the work string during hoist operations. Based on the PNC logs, additional perforation and selective stimulation were made in many wells which, in most cases, improved their net oil production. Additionally, various cost reduction measures were applied to reduce the operating cost per barrel. One of them was a novel idea to use the coiled-tubing unit for cleanout, logging, mechanical water shut-off, perforation, and stimulation in one intervention. This paper describes this single rig-up coiled-tubing process that has eliminated multiple entries and resulted in both cost reduction and improved turn-around time.
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