Mature Fields
Overcome obstacles in mature field re-entry wells to reach total depth
Ecuador
Running casing to planned depth continues to present unique challenges in wells of mature fields as deviations increase and re-entry well designs grow more complex. Selecting the correct centralizer to travel through the window is vital to reduce the potential for becoming stuck because of mechanical integrity failure of the centralizer or stop collar. Challenging conditions for cement placement, such as long openhole sections, washouts in shale intercalations, and equivalent circulating density (ECD) limitations in depleted intervals, worsen with an active aquifer formation. These challenges, often encountered in re-entry wells of mature fields, require a tailored barrier design and application of comprehensive best practices.
EP Petroecuador launched a drilling campaign of three re-entry wells as part of a production increase program. This was the first drilling campaign of re-entry wells managed by HPM as an integrated project. The lateral branch of each well was longer than 3,000 ft, had a deviation greater than 45° of inclination, and would be drilled along complex lithology intercalations. These challenges made it difficult to run the liner and achieve successful zonal isolation because of a combination of washouts, swelling formations, tight spots, depleted zones with low fracture gradient, and a sandstone with high active aquifer. The risk of not reaching planned depth was great because packing off and severe tight spots had to be overcome while tripping to surface with the RPT reamer shoe bottomhole assembly (BHA). The production liner needed to be run without an additional conditioning trip after pulling out of the hole (POOH) the BHA, and reliable barriers were necessary along the primary and secondary production zones distributed in the long open hole. Achieving the necessary top of cement (TOC) and preventing water influx during cement setting was critical to executing successful production testing and well completion.
liner string prevented additional costs
hours of rig time saved during liner run
USD saved per well
The tailored barrier design in combination with centralizers and RPT reamer shoe technology delivered a successful casing equipment solution to achieve the planned depth in the challenging re-entry well conditions of this mature field. The liner, with 96 centralizers, successfully traveled through the window and was run to bottom. The heavy-duty, single-piece centralizer design required zero running force and allowed two centralizers per joint. The RPT reamer shoe enabled wellbore cleaning and conditioning while running along the open hole. Additionally, the reamer shoe and float collar included Super Seal II™ floating equipment run with the temporary autofill activated, saving 1.5 hours of rig time during the liner run.
The cementing service was executed according to the design of service, rotating the liner string throughout circulation and cementing in two of the wells. Barriers were confirmed using cement evaluation logs, and the TOC achieved was close to that expected, as validated using a 3D displacement efficiency assessment. Effective isolation was realized along the active aquifer on bottom, and a dependable cement sheath was obtained in different pay zones on each well. In the two instances wherein rotation was performed, cement sheath was effective, even in washouts.
Because the long re-entry sections were completed using a single liner string, additional costs and complications were avoided in each well completion of the campaign. This allowed the operator to save an estimated USD 250,000 per well.
