Production Enhancement by Creating a New Shut-in Criteria and Process for Drilling New Wells without Jeopardizing HSE, Case Study- Abu Dhabi

Abstract

Onshore Drilling practices implemented in the past in congested environment had established the need to shut the surrounding gas wells within 2 km radius for time period of 3 weeks prior and during drilling of relevant reservoirs of the new well. This very conservative contingency process led to a significant reduction of gas production affecting meeting the targets. This study aims to determine the optimum drainage radius of gas wells to minimize the production deferment along with other operational risks without sacrificing safety. Drilling activities in a giant field has embedded many challenges. One of the major challenges is the one related with managing wellbore stability while drilling various reservoirs with different pressures, whereby the pore and fracture pressures are used as an important factor to design the mud weight to guarantee an optimum wellbore stability; however near-by wells either producers or injectors under flowing conditions would influence the severity of unexpected drilling issues such as mud losses and/or gas kick while drilling new wells, since the collateral effect of the pressure drawdown would affect the vicinity of the new well being drilled affecting the reservoir pressure established on the well design. A detailed study was carried out assessing the impact of the drainage radius of the surrounding gas wells while drilling a new well; considering the whole range of rates and permeability found in the depletion or recycle reservoirs including also the shut in time period of the surrounding wells as an important additional variable. The drainage radius of gas producers and injectors (vertical and horizontal) were estimated using single gas phase pseudo steady state radial flow equations and bottom hole pressure surveys test data plus operational issues previously encountered. Meanwhile, the dimensionless radius, pressure and time were used to estimate the stabilization time required shut in period to reduce the collateral effect on the new well. Accordingly, a new criterion was developed to minimize the gas and condensate production impact taking into consideration the real effect that would be created by drilling a well within the 2 Km radius, assessing pressure variation on the wellbore radius considering permeability variation (100 – 30 – 1 md) along with Flow Variation (gas rate: 40 – 15 – 5 MMscf/d). Several sensitivities and analysis were made ending with very interesting conclusions along with a new shut in well selection criteria, including flow diagram with action parties, roles and responsibilities, and deliverables. The aim of the new process is to set a communication protocol between action parties and optimizing the number of surrounding wells to be shut-in. The New Offset Wells Shut-in Criteria developed for Drilling New Wells was implemented successfully without sacrificing safety, but also saving 46.5 Bscf of gas production, 2.6 MMstb of condensate and 4.5 Bscf of gas injection per year (i.e. 751 MMUS$/year). In addition, the New Process resulted-in maximizing the utilization of the shut-in period to conduct the reservoir monitoring plan activities as well as better planning for production / injection optimization and compensation while adding an important know how effect within ADNOC Onshore being applied as a model for other areas with similar challenges successfully. Proudly present this paper as an enhancement made on the gas wells shut-in criteria; designed fit for purpose for the gas reservoir types either for recycle or depletion reservoir modes link with an optimum drilling operations and production processes.