Offline Cement Evaluation: Boost Cost Effectiveness by Planning Efficiently
Authors: Zayani Siraj , Mohd Johan Mohd Alham , Shahril Shakri Shaifi , Ibrahim Zulkifli , Mamat Muhamad Aasif , Awal Adli Zaim , Zulkefli Siti Nor Dahliawati , Fadzalisham Irfan Zulfadhli 
Published: October 2023

As part of the end life cycle of mature oil-producing fields and fulfilling the license obligation to appropriately abandon wells that are no longer required for petroleum operations within the Production Sharing Contract (‘PSC’), idle wells are evaluated and, if established as having no more potential to produce currently or in future, the wells will be defined as Plug and Abandonment (‘P&A’) wells. The selected P&A wells are included in the planning to ensure that an appropriate P&A roadmap can be achieved within the given timeframe. This paper defines the principal aspects of the planning and execution of the first P&A campaign. Various options have been evaluated with the objective of reducing operational uncertainty which eventually minimizes execution cost. This P&A campaign was optimized by a different upfront identification approach utilizing a through-tubing cement evaluation ahead of an online Hydraulic Workover Unit (‘HWU’) campaign, simplifying the execution and giving better planning on running remedial work if needed, such as perforate, wash and cement (‘PWC’). Low-cost, conventional cement bond log (‘CBL’) tools are available in the market, but they are limited to be run only after [retrieving] completion and therefore increasing standby duration of contingency remedial resources and incurring cancelation charges if not used. As mitigation, a through-tubing cement evaluation as replacement for the conventional deployment method that meets program objective is utilized while also indirectly helps achieve a better contracting strategy, establishes known well complexity, and provides a different strategy for P&A planning. In this paper, the conventional P&A method is compared with the implemented solution of the offline operation adopted for best practice applying optimization strategies. The through-tubing cement evaluation using neutron logging technology eliminates the need to recover the tubing, thus giving opportunities to have the evaluation done in advance. With the capabilities to run via slickline conveyance, an offline campaign was introduced to assist in better logistic planning and time saving. The result of this through-tubing cement evaluation is then being compared using three direct comparisons which use old CBL data done during original well drilling, new CBL data done recently, and the estimated top of cement calculated during drilling on three wells.

The offline operation reduces uncertainty, providing valuable information during the pre-work giving ample time to strategize and plan for the P&A campaign. The need to have all the necessary equipment and crew for E-line and PWC on standby can now be abolished. As a result, cost cancelation can be avoided and in addition significant cost optimization can be achieved. [AEP1]The new strategized approach for P&A integrating cement evaluation done offline during the pre-work reduces the uncertainty thus helping for a better planning.