A Critical Review of Chirag Field Completions Performance—Offshore Azerbaijan B

Abstract

Chirag field was the first of three fields put into production in the Azeri -Chirag -Guneshli (ACG) megastructure, located in the Azeri sector of the Caspian Sea and operated by BP on behalf of Azerbaijan International Operating Company (AIOC). Production commenced in late 1997 after completion of the Chirag A01T1 well. A number of different sandface completion types have been installed in Chirag injectors and producers during the Chirag Early Oil Project (EOP), and significant data have been collected to evaluate the performance of each completion type. Completion types include cased and perforated, open hole gravel packs (OHGP) using wire-wrapped, pre-packed and alternate path (shunttube) screen technology, stand-alone porous metal fiber premium screens, and expandable screens. To date, 29 completions have been installed in 19 of 24 available well slots in primary and sidetrack wells.Many of the producing wells are equipped with permanent downhole pressure-temperature gauges, the flowlines are equipped with acoustic sand detection devices, and an active separator production test and surveillance program has resulted in a quality data set to evaluate completion performance under initial "dry oil" (water free) conditions, and upon the onset of produced water. This quality data set has greatly assisted the completions performance analysis, which has helped shape completion decisions and technology requirements for full field development.The paper will review the completion evolution in Chirag field, the relative performance of completion types over a broad range of indicators, and will include a discussion about measures taken to improve open-hole gravel pack performance from a reservoir damage perspective, with a focus on producers.

Openhole Gravel-Pack Case Histories Using Alternative Fluid Displacement for Synthetic-Based Mud

“…The open hole is displaced to brine, viscous fluid, or fresh reservoir drilling fluid (containing bridging agents sized to flow through the screens), and cased hole is displaced to brine. Gravel packing is then performed with brine [see Ali et al (1999), in a low-inclina-tion well] or a viscous fluid in conjunction with the shunt-tube technique (Ofoh et al 2006;Chambers et al 2000;Powers et al 2006). Although used successfully in some cases, this approach may result in an inability to run the screens to target depth because of shale swelling and/or collapse, as documented by two operators (Powers et al 2006;Hecker et al 2004), or in poor productivity because of mixing of shales with gravel during gravel packing, requiring post-gravel-pack cleanup treatments, as documented by another operator (Ali et al 1999).…”

“…Subsequently, the screens are run in hole, and the SBM in the openhole section is typically displaced with a SF, water-based viscous fluid. In some applications, the cased hole is displaced to brine before gravel packing with a viscous carrier fluid (Powers et al 2006;White et al 2008), and in others, the SBM displacement from the casing/work-string annulus takes place during gravel packing (Hecker et al 2004). In the latter approach, the water-based-fluid volumes used for openhole displacement and while spotting the slurry in reverse position are adjusted such that the entire casing annulus would be displaced to water-based fluids by the end of the gravel-pack treatment (Hecker et al 2004).…”

“…In one case, the gravel-pack carrier fluid is spotted into the casing/work-string annulus in reverse position, and the SBM is displaced by pushing the viscous fluid down through the casing/work-string annulus, down through the washpipe, out the screens, up through the openhole/screen annulus, and up into the work string (Hecker et al 2004). In the other approach, SBM is displaced in the normal gravel-pack position and direction (i.e., down through the work string, crossover ports, and openhole/screen annulus, and up through the washpipe and up into the casing/work-string annulus) (Powers et al 2006;White et al 2008). In both cases, the shunt-tube technique has been used for gravel packing (Hecker et al 2004;White et al 2008).…”

“…A reversible SBM was selected for reservoir drilling-SBM because of reactive shales, and reversibility for proper filtercake cleanup to ensure production targets are met. The alternative-path technique was selected for gravel packing because of its track record in gravel packing of wells drilled with SBMs/OBMs (Powers et al 2006;Hecker et al 2004;White et al 2008) and the low fracturing gradient of these reservoirs.…”

A Comprehensive Study on the Effect of Compliance on Productivity

“…Some examples of these are a comparison between the long term performance of SAS, OHGP and ESS in the Mokoko Abana Field 2 , a comparison between frac-pack and ESS in the Kikeh field 3,4 the performance of ESS in gas condensate wells in the North Sea 5 , and a comparison between various completion options in a Caspian Sea field 6 .…”