The recent decline in the price of crude oil has necessitated more cost effective ways to sustain and increase production worldwide. From July 2014 to May 2015, Addax Petroleum Development Nigeria Limited (APDNL) embarked on a successful re-entry campaign in its shallow and deep water fields. These wells' Vertical Lift Performance (VLP) had been compromised by excessive sand production; rather than drilling new wells to recover the trapped reserves that would otherwise not have been produced by the impaired wells, it was more optimal to re-enter the existing wells, recover their completions accessories and then side track into optimal locations within the reservoirs of interest. These suboptimal wells were not considered for recompletion because in addition to excessive sand production, increased water cut and Gas Oil Ratio (GOR) meant that the drains were no longer in the best positions within the reservoirs to produce the trapped oil estimated to be left in the reservoir. The new side track wells would have their drains placed higher in the reservoir (based on production data from the soon-to-be-abandoned wells), but would not bear the full costs of drilling new wells nor their associated future abandonment liabilities. Seven wells were re-entered during this period and side-tracked in cased hole with the use of hydraulic whipstocks, none of the side tracking operations witnessed significant down time. The whipstock was deployed to its intended setting depth, casing window milled and additional rat hole drilled in one trip. Each phase in the whipstock operation had inherent risks and challenges that were successfully managed by identifying these risks early in the planning phase and mitigation steps put in place to ensure the operations were carried out with minimum Non Productive Time (NPT) as the cost implication of an operational mishap would have been severe. This paper reviews the re-entry operations performed, challenges encountered with deploying hydraulic whipstocks. It also identifies the Key Performance Indicators (KPI) used to benchmark and compare the operational performance. Finally, this paper highlights the lessons learned during the re-entry campaigns and measures put in place to optimize future operations with respect to deploying whipstocks.

The decision to drill new expensive offshore wells is made because of the availability of information that proves the profitability of these new wells and the possibility that these wells can be drilled faster and more efficiently due to experience that has been gathered from drilling older wells under similar conditions. The cost of drilling new offshore wells has not reduced in recent times and drilling new wells to meet production targets has become more challenging while well trajectories have become increasingly more complex thereby increasing the associated costs of delivering such wells. However, new technologies combined with experience have improved the efficacy of operations when drilling relatively challenging wells. Addax Petroleum Nigeria in its offshore OML-126 operations has been able to overcome technical, logistical and organizational challenges by effectively applying lessons learned from previous operations in its on going operations there by improving drilling performance – reducing time spent drilling and operational costs. Simple modifications such as using a 36″ bit instead of a hole opener to drill the top hole section improved cementing, setting the seal assembly after cementing operations rather than before cementing to prevent the accumulation of debris around the seal assembly area improved the efficiency of setting the seal assembly, optimizing the screen sizes while drilling the reservoir section reduced the time spent conditioning the mud to Production Screen Testing (PST) quality for completion operations (running Expandable Sand Screens (ESS) and Stand Alone Screens (SAS)), and has also considerably reduced the time for completion operations, other factors like continuity, in-house competition, improved communication and knowledge management has helped increase the efficiency of operations and saved cost». This paper expounds on these and other changes that were carried out during the Phase I development of the Okwori field and how they reduced costs and saved time while achieving the goals that were set prior to commencing the drilling campaign.

In a regime of volatile oil prices, it has become increasingly important to plan and deliver cost effective wells safely. Typically, this is achieved by optimizing technical details in planning and execution phase; however, an often-overlooked area of optimization is the management of rental tool inventory and the associated logistics. This area is usually subject to cost overruns due to insufficient tracking of equipment from mobilization through its use at the rigsite, resulting in late demobilization and incurring of additional cost by operators. To completely eliminate these unwanted costs, a web/intranet based, equipment tracking solution which interfaced with the existing enterprise resource planning (ERP) platform (for contracting and procurement information) was designed and implemented by Addax Petroleum Nigeria to track and monitor the movement of rented equipment between service providers, logistics base and operations base. It ensured the effective tracking of rented equipment upon mobilization up till demobilization; this helped to prevent cost overruns for rented equipment during the drilling campaign. Daily reports and notifications were also provided to all key personnel on rented equipment status and it ensured a collaborative workspace for drilling team members to manage rented equipment movement internally. The rentals inventory tracking application (RITA™) software was deployed during a six-month drilling campaign in 2017/2018. It provided comprehensive tracking for equipment mobilized to the rig, eliminating cost overruns on rental equipment throughout the project and cost savings of circa $1,000,000 during the six-month drilling campaign.

It is possible to conduct a drilling and completion operation, sustaining a high operational performance and ensuring low Non-Productive Time (NPT) throughout a well drilling and completion campaign. The results from a recent onshore drilling campaign proves that with the right people, planning and process, a hitch free drilling and completions campaign can be achieved. In this case a perfect campaign was defined as;Delivering the planned work-scope (5 wells) within the approved Authority for Expenditure (AFE) cost and duration. Drill to the specified Total depth, penetrating all the subsurface targets within the stated tolerances specified. Achieve less than 15% overall non-productive time.Deliver the planned work-scope without Fatalities (FAT), Loss Time Injuries (LTI), Restricted Workday Cases (RWC), or uncontrolled discharges to the environment.Deliver wells without well control issues, Stuck-pipe incidents or any train wrecks.Deliver wells with minimal formation damage.Maintain technical and operational integrity by complying with statutory regulations and company governance documents always. In order to avoid previous problems encountered while drilling the appraisal wells, critical sections of the Well delivery process were thoroughly reviewed and optimized as required. These include: The Well Design, Rig selection/certification and acceptance, Safety, and drilling operations and logistics. The optimization methods are extensively discussed in this paper. The improvement and close optimization of the mentioned facets of the project helped to save circa $14MM from the project. When compared with other land projects in the same terrain (Niger Delta), the campaign was observed to be a top performer in the P-10 region of the performance percentile.

The deployment of a coiled tubing (CT) conveyed cement packers for accessing bypassed hydrocarbon/ marginal reserves through rigless through-tubing well intervention presents economic potential for mature field access and optimization. They provide a good means of zonal isolation of the last reserves in an existing wellbore. However, zonal isolation is challenging in highly deviated wells. These shortcomings are predominantly related to slurry density control, displacement efficiency, well architecture (completion jewelry), poor cement bonding in the annulus between the tubing and production casing, and issues with pulling the CT out of hole while maintaining the differential pressure between the well head and casing head pressures (estimated top of cement in the casing annulus). Recently, the application of liquid cement latex (LCL) additive for cement packer completions using CT has shown remarkable success. LCL cement additive is a liquid additive designed to lower equivalent circulating density (ECD) and impart excellent fluid-loss control, high-temperature suspension properties, and acid resistance to cement slurries. This paper summarizes the operational and logistical process of executing a cement packer with conventional cement and LCL additive in a highly deviated well, offshore Niger Delta. In addition, the applications, features, and benefits of LCL with associated spacer fluid is detailed. The operational and logistical benefits of using LCL is discussed, concentrating on its ease of transportation and pumping, minimal equipment requirements, consistent slurry properties, and reduced environmental exposures. Best practices recommendations are also be made for cement packer placement, supported by the executed successful deployment in the offshore Niger Delta using LCL.