A Novel Fluidloss Control Pill That Works Without Filtercake Formation: Applications in High Rate Gas Sub-sea Frac and Pack Completions in Indonesia

Abstract

Abstract Loss of completion fluid during a completion or work over operation not only increases the chance of losing control of the well, but also can severely damage the formation. The best industry recognized method to stop fluid losses into the formation is to use mechanical fluid loss control devices. However, sometimes, the use of mechanical fluid loss control device is not applicable. Two examples where fluid loss control devices are not applicable areShoot and Pull Tubing Conveyed Perforating (TCP) before a gravel pack or a frac pack, andSingle trip perforating and gravel pack or frac pack completions. In these cases the use of fluid loss control pills is necessary. Traditional fluid loss control pills are associated with formation damage, clean up trips and annular pack plugging. This paper presents the application of a Viscoelastic Surfactant-based non-damaging lost circulation pill (VES-PILL) during the completion of sub-sea gas wells in the South China Sea for ConocoPhillips. This novel solids-free fluidloss control pill was applied to insure well control after perforating and before frac packing. This paper describes the cases from the two wells of which one was completed as a single trip multi-zone frac and pack completion and the other as commingled stack frac packs. These commingled stack frac packs consisted of multi-zone frac packs and gravel pack on bottom and a conventional frac pack on top. Both single trip completions considerably exceeded the world record for the longest single trip gravel packed completion. In the first well, well control was achieved and the losses were controlled from 322 bph to 8 bph. In the second application, during a traditional shoot and pull, the losses were controlled from 60 bph to 0 bph. After completion, the wells were tested at 87 and 55 MMSCFD at 400 psi WHP, and were found to exceed pre-drilling production estimates by about 17–24%. This further confirms the non-damaging property of this VES-PILL. Introduction Fluid loss control is considered a very important practice during any workover or completion operations. Excessive loss of completion fluids might result in well control problems, formation damage, hole instability and/or increased completion cost.[1] The best option for this is to avoid using fluid loss control pills by incorporating mechanical fluid loss control devices into the completion string whenever possible.[2] However, in some wells, mechanical fluid loss control devices are not applicable. In these cases fluid loss control pills represent a viable option. Fluid loss pills control leak off into the formation by one of the following three mechanisms. The first mechanism is the viscosity of the pill, which has a lower leak-off coefficient to the formation than the completion fluid. The second mechanism is the plugging and reduced leak-off by the use of sized solids in the fluid loss pill. The third mechanism is the formation of filter cake in the porous rock media or on the rock surface. Fluid loss control pills are generally composed of very high concentrations of crosslinked polymers with or without bridging particulates.[3] These fluid loss pills can lead to the damage of the perforation tunnels, the reservoir and the proppant pack in gravel pack completions. Polymer residues that remain in the proppant pack adversely affect its permeability, impairing the productivity of the well. The utilization of polymers in the pill not only increases the risk of formation damage but also, in most cases, requires extra operations for clean up and removal. Sized solids can also be used to minimize losses; however its use can further complicate the system as it requires additional cleanup stages depending on the nature of the solids used.