Abstract
Abstract
Horizontal wells with long laterals and Inflow Control Device (ICD) completion drilled from artificial islands are adopted in an offshore field, UAE to boost hydrocarbon production from high-temperature Arab formation. High-temperature conditions, long lateral, heterogenous reservoir, ICD completion, and dolomitic formation provides harsh environment for a successful acid stimulation treatment. Previous interventions with regular 28 wt% HCl and conventional emulsified acid were conducted in one of these oil horizontal wells. Both acid treatments failed and resulted into no incremental production. The horizontal well was completed across a long lateral of 5,200 ft with 4 ½ in. liner equipped with ICD system with a high bottom hole temperature of 300°F, permeability range of 0.3 to 40 md, and average porosity of 15%. In this paper, we will discuss how the application of the new polymer-free, single-phase delayed acid fluid (PFDA) technology unlocks the full production potential of Arab formation.
Extensive laboratory testing including diffusivity testing, coreflow testing, and computed tomography scanning was conducted to evaluate the performance of the PFDA against regular HCl and emulsified acid. These tests proved that the use of PFDA would enhance the acid penetration in the dolomitic formation due to the retarded rate of reaction, maximizing reservoir contact. The tests also proved that 20% acid strength would be effective to create long dominant wormhole, bringing advantage to reduce corrosion package compared to the previous treatment using regular 28% HCl
The low friction of the new polymer-free, single-phase delayed acid (PFDA) enabled high pumping rate through Inflow Control Devices (ICD) completion during the entire treatment, which was previously a challenge due to high viscosity of emulsified acid. The PFDA was combined with a viscoelastic surfactant-based diverter to maximize lateral coverage in the heterogenous reservoirs. Software modelling was coupled with the extensive testing and the PFDA fluid technology to optimize job design, volumes, pumping rates, and diversion strategy. The integrated approach yields unprecedent stimulation success.
Post treatment analysis showed that the PFDA boosted the production by more than 1000 BOPD (140%) compared to no incremental production from previous acid stimulation treatments with conventional emulsified acid. The use of PFDA enabled high pumping rates up to 20 bpm compared to 12 bpm for emulsified acid, reduced the mixing time by 16 hours, and saved on associated cost and time.
The introduction of the new PFDA provides the industry a revolutionary fluid technology to unlock the full production potential of Arab carbonate formation. Moreover, the polymer-free, single-phase delayed acid simplifies operations, eliminates the need for diesel phase and associated HSE concerns, and reduces carbon footprints.