Production Improvement for Horizontal Wells in Sumatra

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. ProposalSeveral horizontal wells have been drilled in different sandstone formations in Sumatra. These formations have a typical permeability of 100 to 500 md, a low bottomhole pressure (BHP) of 450 to 750 psi, and a bottomhole temperature (BHT) of approximately 200ºF. The wells are completed with perforated liner. The objective of the horizontal drilling program was to increase oil recovery in low-permeability estuarine reservoirs. Some of the drilled horizontal wells did not perform to expectations and an intensive study was undertaken to identify completion and stimulation opportunities to increase production.During this study, all aspects of the initial completions were examined and redesigned.1. The drill-in mud was reformulated to reduce the amount of polymer and increase the use of fine calcium carbonate to decrease lost circulation during drilling and simplify the removal of filter cake during initial completion. 2. Core tests were performed to identify the optimum fluid formulation, which dissolves the remaining filter cake but does not destroy the formation's natural permeability. 3. A new way of removing the filter cake after completing the well was introduced using oxidizer technology. 4. A new, true fluidic oscillator was used to remove nearwellbore skin (in conjunction with an improved acid system) for wells that have been producing for several months or years.The paper presents several case histories to discuss how completion and stimulation problems were systematically evaluated resulting in increased horizontal well production.

Horizontal Drilling Application to Recover Incremental Oil in Low-Permeability Carbonate Reservoirs, Partitioned Neutral Zone

“…3 Also observed was that the oil in the low permeability intervals could not be effectively and economically drained by vertical wells under primary production and secondary recovery with waterflood in the cases of the Minas, Bangko, Bekasap and Daqing fields. 4 This observation is illustrated in the reservoir surveillance log shown in Fig. 8.…”

“…If invasion of polymer fluid into the sand face of the lateral occurs, removal of the skin damage caused by polymer products and plugging particles such as drill solids, clay, barite, rust, etc, n the drilling fluid can be extremely challenging. 4 A water base drilling fluid system was used for the horizontal drilling in the low permeability Ratawi Oolite carbonate reservoir. This is a low fluid loss system, which uses CaCO 3 particles as bridging agents and an extra refined polymer system consisting of dispersible Xanthan gum and starch polymers.…”

Enhanced Rocker Tool used to Restore the Permeability of Formations: Case Studies

“…The high performance and success rate of the TFO in case studies (McCulloch et al 2003;Gunarto et al 2004;Harthy et al 2004;Hegazy et al 2007) can be attributed to a synergy between the chemical effect of the fluid treatment being pumped, the mechanical action of the pressure waves, and the focusing effect of acoustic streaming. The action of chemicals is enhanced by the increased contact area with the formation.…”

“…The TFO delivers treatment fluid to the formation and combines the cleaning effect of cyclic loading by pressure waves, acoustic streaming for pinpoint placement of the fluid, and the synergistic effect of chemical treatment enhanced by increased fluid mixing and larger area of contact. Gunarto et al (2004) reported a significant increase in productivity after applying the TFO in horizontal wells in Sumatra. In the field evaluation, filtercake solvent was pumped into horizontal wells in a field located at the UK section of the North Sea using TFO and CT equipment, yielding a 62% production increase.…”

Fluidic Oscillation Technique in Conjunction with Acid Stimulation Improves Gas Wells Productivity

“…3 There was also a history of using the tool successfully in Egypt for a different operator. This tool has been used successfully by several operators around the world.…”