Cluster drilling comes with its own attendant challenges; however, operators usually adopt this option in order to reduce environmental footprint and optimize cost. Drilling additional wells in an existing cluster will require simultaneous operation in order to maximize value. The philosophy underlying the rules for SIMOPS is that the interactions between operations must remain manageable (and can be demonstrated to be so) under all conditions that can be realistically foreseen. This paper focuses on four (4) activities that delivered the Ogini field HSE-Case, whose primary objective was to generate an in-house risk assessment and hazard register for Simultaneous Operations (SIMOPS) involved in drilling of the five (5) new Ogini wells namely:- Operational description of Ogini SIMOPS project, Description of HSE-MS, Risk Assessment and Remedial Action Plan (RAP). The SIMOPS for Ogini-field was limited to those activities associated with oil production from the existing wells, drilling operations and laying of flowlines for tie-in of new wells to the flowstation for production. The Ogini SIMOPS have several HSE components that require critical review; a multi-disciplinary team was constituted to assess/evaluate the Risks and generate a Hazard register used in Simultaneous Operations Planning (SIMOPS) for the project. The Scope of work of the team included coming up with the industry-acceptable strategies to carry out the following operations simultaneously viz:- Flowline Construction, Rig Move, Well Delivery and Production. A SIMOPS Planning was developed by NPDC Team and approved by DPR. Five (5) horizontal wells were drilled in a cluster (of 4.5m apart) with two producing wells; hooking up the new wells to production facility sequentially while rig was still on site. Following the review of the distances between the planned five wells and considering future intervention works in this location, after drilling and completion of first two wells, the rig was skidded some meters further away from the initial surface location to drill the subsequent wells. Extended well test was carried out on these completed wells during this operation. This reduced the identified risks associated with SIMOPS and also provided accelerated returns on initial investments.

Over the years horizontal wells have been drilled using the conventional approach. Failure to drill and place the horizontal drain section optimally was becoming a common occurrence especially in a thin reservoir. The search for processes and procedure to mitigate this failure led to the creation of Well Placement (Geosteering) Process. This process was defined (Rogger Griffit 2009) as "The planned interactive placement of the well-bore using geological criteria and real-time measurements". Using geological criteria in real time requires technology capable of adequately delineating the structure and at the same time providing Petrophysical properties of the reservoir in real time. These needs led to development of key Logging While Drilling (LWD) technologies for high angle and horizontal wells. Over the years, the Geosteering methods have evolved based on available LWD technologies. These methods have been classified as (i) Reactive (Basic log correlation), (ii) Proactive (Distance to Boundary) and (iii) Strategic Reservoir mapping). The objective of this paper is to demonstrate how technologies were utilized in Ogini campaign to optimally position the production section of the wells close to the reservoir top, so as to delay onset of water, reduce intervention cost and to increase ultimate recovery. To achieve these objectives despite high risks due to structure and stratigraphy, two well placement methods / technologies were deployed in the landing and within the production section of the reservoir. Real Time Image/dip technology was utilized in the landing section to aid the landing while monitoring the apparent formation dip and a Multilayer Distance –to-Boundary technology (PeriScopeHD*) was used to optimally position 5 horizontal wells close to the tops of each of the target reservoirs in Ogini field.