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Drilling operations are conducted within a pressure window bounded on the lower side by the pressure of the formation fluids exposed in the open hole and on the upper side by the fracture resistance of the formation matrix. The narrowing of this operating margin, as experienced in deepwater environments, increases the technical challenges associated with drilling operations. Typical challenges include a sharp reduction in the maximum allowable open hole drilled depth, well control and exposure to difficult kicks, well breathing or ballooning, the risk of wellbore losses and a requirement to install multiple casing strings to get to TD. This paper examines the phenomenon of narrow margins in deepwater, the conditions that drive it, and presents a holistic assessment of the available geological, geophysical, engineering and technology solutions for mitigating narrow margin drilling (NMD) conditions. The solution concepts are indexed into a newly developed model called the NMD Solutions Matrix which introduces an NMD intensity scale that provides a measure of the degree of difficulty that can be expected in a well as a result of narrow margin conditions. The applicability of the model is demonstrated in a history match of three industry case examples in two deepwater regions in the world where NMD conditions were encountered and mitigated. The NMD solutions matrix was also applied to a DW project in the planning phase which yielded insights that more clearly articulated the exposure in the project. The analyses indicate that the model, as a planning tool, has the potential to sharpen the awareness of possible challenges and enable upfront mitigation measures to reduce their impact during execution. Its application thus offers strong potential to positively impact drilling effectiveness in deepwater and yield or save considerable value in these high cost operations

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Horizontal wells are susceptible to early water breakthrough (EWBT) due to reservoir heterogeneity and "the heel-toe effect", caused by frictional pressure losses along the well that lead to a non-uniform production profile. Also, with heavy oil reservoirs, early water breakthrough can occur because of viscous fingering due to an unfavorable mobility ratio caused by a difference in the viscosity of heavy oil and water. This ratio leads to a high inflow of water into the wellbore. EWBT is undesirable as it brings with it negative implications; from low oil productivity to corrosion in the wellbore and water disposal challenges. There are different industry solutions to managing early water breakthrough including reservoir based improved oil recovery (IOR) or enhanced oil recovery (EOR) methods such as thermal EOR (steam flooding, cyclic steam injection), chemical EOR (polymer or alkaline flooding) or miscible EOR (with methane or ethane to reduce capillary resistance). These methods are however complex and broad field-based applications with varying experiences in the outcomes of the field implementation. There are also mechanical well specific solutions for mitigating EWBT and in this paper, we present the considerations and plans for the application of Autonomous Inflow Control Devices (AICDs) for the mitigation of EWBT in the Niger Delta. AICDs are relatively new and are known for autonomous selective choking of fluid phases. They restrict the flow of less viscous phases like water while allowing more viscous phases like heavy oil to pass through, with minimum pressure drop. The paper examines the different causes of EWBT in Ogini field and the different solution options available. It presents the cost/benefit analysis and modeling considerations resulting in the selection of AICDs for EWBT mitigation. The paper concludes with the technology implementation plan developed for its successful deployment in the upcoming drilling campaign.

With the vision to improve production in SPDC by 20% (to over 1.0MMbopd) in the short term coupled with incessant community disturbance &the thrust to reduce environmental impact, most new wells favour utilising existing facilities and innovative technology to reduce cost &boost production. Expandable Tubular Technology (ETT) was one the key technologies identified for to achieve this. Over 150 wells were identified for this technology in the medium term with 3 wells selected as quick wins for deployment of the SET in 2001. The selection criteria were based on low risk, reduced unit technical cost and the need to extend the envelope of the technology. This paper focuses on the challenges encountered in the planning &execution phase. It addresses the contracting, procurement and logistics constraints associated with the first deployment of the technology outside the Gulf of Mexico. It emphasises the engineering considerations applied to assess the technical feasibility of deploying SET. The applications also utilised a novel cementing technique "Settable Spotting Fluid" from Halliburton to minimise the risk of cross flow &low side channelling, a common situation in high angle applications in the Niger Delta. Finally, It reviews the economic justifications and highlights the value of the technology (accelerated production, reduced risk cost &lost opportunity). The challenges encountered and mitigated during execution climaxed with the installation of the World's first horizontal Open Hole Liner (OHL) in Agbada 1ST. The successes have now extended the application of the technology from the current 20% of the global market to 80% of the global market (high-angle/horizontal wells) with a thrust of revolutionizing the concept of well delivery. What is SET? Expandable Tubular Technology or "Xwell" technology is a Shell group initiative to achieve a step change in drilling operations. It is grouped into Expandable Slotted Tubular (EST) &Solid Expandable tubular (SET). EST's are pipes with staggered but overlapping slots cut axially along its entire length(1). Expansion depends on the dimension and placement of slots and the size of the expansion cone. Expansion principle is based on bending the metal strips between two overlapping slots(1) thus requiring small expansion forces (~ 10 tons). SET on the contrary involves the cold working of steel to the required size at down hole conditions. It expands based on the principle of 3-D plastic deformation of the material and expansion forces are in order of 10–30 times that of an average EST(1). SET can be utilised in all facets of well life (drilling, intervention &abandonment). It has the potential to reduce the unit development costs by significantly down sizing wells, improving opportunities for complex designs (side-tracks/ML level 6), extended reach drilling and economic exploitation of oil and gas in hitherto uneconomic and hostile environments(2). In offshore operations it serves dual purpose; it can be used to reduce riser size thus necessitating a lower cost semi/drillship. In onshore operations, lighter capacity rigs could be used to deliver wells without a loss in potential. Background SPDC's drive to increase &sustain production at over 1.00MMbopd at reduced Unit Technical Cost favoured accelerated production achievable through the drilling of high-rate wells. Asset teams through the Volume for Value campaign (V2V) identified several candidate wells &in line with the drive to minimise the impact of oil exploitation to the environment (reduced land uptake, efficient and effective waste management, community disturbance etc), horizontal side-tracks were favoured to achieve this goal(2).