Saldungaray et al. recognized that proppant-filled perforations can become a dominant restriction to flow in high productivity wells. In the Widuri field in the Java Sea, a deviated open-hole completion was successfully frac-packed with good results.
Although frac-packing has been widely and successfully used in cased-hole completions, open-hole frac-packing is not so common. It is well known that the efficiency of cased-hole frac-packs can be limited by the perforations. It can therefore be expected that open-hole frac-packing would provide higher productivity by eliminating a major choke in the flow path. In this paper, we present an open-hole frac-pack case history involving a highly-deviated, challenging well in South East Asia and demonstrate the expected efficiency gains.
The well was drilled in a field with a major water-flooding program. Due to extremely low reservoir pressure, low fracture-gradient and high kh formation (100,000 md-ft), very high losses were experienced. The presence of a high-pressure, reactive shale above the pay zone made it necessary to prematurely run a 7-in casing in order to isolate the problematic zone. However, due to the collapse of the reactive shale section, the casing was set above the target depth thereby exposing 70-ft of shale zone. Initial attempts to run the completion assembly failed due to the collapsed shales, resulting in a suspension of the well. After 4-months of water-flooding, partial re-pressurization of the reservoir was expected, and consequently a decision was made to complete the well with the open-hole frac-packing technique. In order to address complete coverage in a high kh zone completed as open-hole, the shunt technique was used. In order to prevent reactive shales from collapsing and mixing with the proppant during frac-packing, a cup-type packer was set inside the casing to divert flow through the shunt tubes and thus bypass the shale section. These procedures resulted in a complete pack of the entire, highly deviated open-hole interval, with an optimized tip screen-out as per design. The resulting PI of 13.4 bpd/psi compares favorably to cased-hole frac-packs (average PI of 2.5 with a best PI of 5.8), cased-hole gravel packs (average PI of 2.3 with a best PI of 4.7) and open-hole gravel packs (average PI of 10.0 and best PI of 19.6) in the same field, particularly considering the extremely high losses (thus the extent of damage) experienced during the drilling stage of this well.
Detailed procedures are given along with operation execution and production results. An extension of this technique to long open-hole horizontal wells (injectors and producers), using modified tool configurations, is also discussed.
Author(s): Schlumberger, Pedro M. Saldungaray, Schlumberger; Juan Troncoso, Muhammad Sofyan, Bambang T. Santoso, Repsol-YPF; Mehmet Parlar, Colin Price-Smith, Gary Hurst, William Bailey
Paper Number: SPE 73757