In this paper, a new carbonate stimulation methodology and its impact to the planning of very long, open hole completions will be presented. While the key objective of stimulation is to connect the well to the reservoir, completion equipment design and related well performance have become more important factors. Traditional methods of stimulation modeling and fluid placement are no longer sufficient for these types of wells. This paper introduces how completion design becomes more complex for more aggressive stimulations. For example, completions with pre-drilled or slotted liners for stimulation with coil tubing acid wash are less sophisticated than ball drop liners for high-volume acidizing or fracturing. In long horizontal completions, computer modeling of stimulation needs to address the flow conditions caused by liners, swell packers and inflow control devices (ICDs). Recent well planning for a long horizontal pilot well (Pilot Well 5) has included the use of new carbonate matrix stimulation software to design a fit-for-purpose completion liner that will accommodate bullhead treatment of a long completion interval. Various completion designs were considered based on objectives from reservoir engineering and geology. Being part of a pilot well program, the strategy is to test fit-for-purpose liners that would balance completion cost with long term productivity and recovery. The well design required more than 100 runs of the new carbonate matrix acidization software to finalize a liner design that employs over 200 holes distributed along the length of the lateral. The final design was developed to accommodate uncertainties in the reservoir properties and allow for safe and reliable rig operations. The resulting design could serve as a lower-cost alternative to ball drop stimulation liners for long openhole completions.

The recent industry development of drilling ERD wells with horizontal laterals in the reservoir of 10,000 ft. or more has led to a greater use of passive flow control devices and swell packers to achieve the desired inflow or outflow profiles. Another desire is to perform stimulation treatments of the lateral especially in tight carbonate formations. However, such treatments can create high velocities through the Inflow Control Devices (ICDs) that inevitably leads to high turbulence and wall shear stress in the ICD which can cause severe erosion and corrosion of commonly used materials. There appears to be little experience and associated knowledge on corrosion mitigation to ensure ICD integrity after well stimulation. This paper will attempt to address such concerns through: Discussing and analysing ICD design considerations to avoid high corrosion areas and selection of high alloy materials to resist corrosion. Selection of appropriate acid system and method to prevent corrosion. Laboratory testing of acid formulations under high wall shear conditions as predicted from Computational Fluid Dynamics (CFD) of the ICD design at reservoir conditions. Laboratory measurements of the performance of corrosion protection additives in acid formulations under wall shear conditions. Other possible mitigation efforts to reduce the need for stimulation treatments. Each of these factors presents limitations which either restricts the use of aggressive acid systems or requires alternative acid systems that can lead to increased treatment cost and/or sub-optimal stimulation of the reservoir through the ICDs. This paper discusses one producing company's effort to systematically improve the overall performance of stimulation through ICDs while maintaining the integrity of the lower completion liner.

For the last 30 years, wells in the field have been suffering from medium to high corrosion rates in both near surface and downhole components. Remedial measures had been implemented in order to restore Well Integrity with different techniques. Corrective actions aside, a strong preventive approach is needed to better understand the root causes of such corrosion rates and scenarios where the integrity of specific wells has been seriously compromised due to corrosion problems.Taking a step further and considering the big implications of new projects such as Artificial Islands project, where the company will be drilling & completing over 300 Extended Reach Drilling (ERD) wells, Well Integrity input as a discipline becomes critical in order to ensure previous problems will not be repeated and all lessons learned throughout the years will be wisely taken into consideration when designing a new well to remain integral during its whole expected life.Understanding of the current corrosion mechanisms in the field was the key to find not only solutions, but also, to create an approach aimed to improve the future completion for Island wells in terms of design, materials and many other factors.An extensive multidisciplinary approach was carried out in order to successfully complete a full study in one of the pilot wells completed with Inflow Control Devices (ICDs), which will be analyzed in detail in this paper, covering the following areas:i. Well design and configuration ii. Well monitoring and performance review iii. Well diagnosis and failure investigation iv. Post-Failure modelling and well prediction v. Preventive/Corrective actions for future wells. Corrosion management and prevention of scale deposits were the two main challenges encountered during this project, which was launched and completed with the main objective of evaluate and optimize the ICD completion design in one Maximum Reservoir Contact (MRC) pilot well in the field, the findings and lessons learnt were used to upgrade the current well design and improve the development plan for the field.

Following a premature failure of an ICD liner in a pilot ERD well in a giant Middle East offshore oilfield, a thorough investigation, summarised in a prior paper1, 2, was undertaken to understand the failure mechanism. The conclusion of the failure analysis was that high shear flow from the ICDs accelerated tubing corrosion leading to a complete penetration of the tubing wall in the vicinity of the ICDs. This paper details the subsequent work undertaken to initially review existing ICD designs currently available from the market to deem their suitability to withstand flow induced corrosion. Initial review of current designs led to the need for subsequent development of improved ICD designs, also detailed in this paper, that could withstand flow induced corrosion, as well as accommodate heightened production (400 - 1,600 psi) and stimulation (1,000 - 2,400 psi) differential pressure requirements. In particular the paper will cover the below areas of qualification, with key outcomes: Engineering design review of existing, improved and new ICDsCFD analysis for flow-induced corrosion hotspot identificationIntegrity testing for production and stimulation scenariosFlow performance and minimum back pressure requirement testingErosion testing of the entire ICD assembly For any of the designs to be suitably qualified, they had to systematically and successfully pass the aforementioned five areas, which in summation is believed to be the most in-depth qualification program undertaken in the industry to date. It has also likely developed the most robust ICD designs to date affording the ability to operate under heightened production and stimulation conditions while still providing the required 30 year life for use in a giant Middle East offshore oil field.

As part of the Islands Project which involves the use of 4 artificial islands to drill & complete over 300 ERD wells in a giant offshore oilfield, several completion designs have been piloted to test & monitor their suitability for the brownfield development. One well design incorporated the use of Inflow Control Devices (ICDs) & swell packers which was ZADCO's first use of such technology in a production well. The technology was installed in the pilot well to test in-flow control along a 10,000ft lateral & to manage future water production. The Paper will cover: The design of the well detailing the ICD configurations & swell packer arrangements providing 15 compartments along the reservoir section, The inflow performance recorded annually along the lateral showing differing results, The outcome of an extensive intervention program in 2013 utilising different logging tools to record internal & external data, live camera to view condition in low water cut well & venturi tool to recover downhole samples that concluded the mechanical failure of ICDs in the heel, The extensive post-failure investigation undertaken such as extensive review of installed ICD design, flow assurance, computational fluid dynamic (CFD) simulations, laboratory testing for different conditions & materials, comparison of modelled with actual data to determine failure mode & The way forward for future ICD installations with initial short term solution & plans for future long term design solutions to give a required 30 year life.