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Drilling high angle wells into a heavily fractured, highly pressured, sour Jurassic reservoir may be the key to unlocking substantial reserves of light oil for Kuwait. One of the main risks to effectively developing this unconventional reservoir is the ability of wells to access a permeable, interconnected, vertical fracture network, without which the oil will not flow. Less than 50% of the vertical wells drilled to date have been successful due to a failure to intersect fractures or due to formation damage suffered during drilling. High angle or horizontal wells, while more technically challenging and expensive, will ensure fractures are encountered and will ideally penetrate multiple large, oil bearing fractures, to provide high productivity and reserves recovery per well. This paper discusses the challenges of designing a high angle well into the Jurassic which has so far proved difficult to drill vertically. These challenges can broadly be divided into three major categories - the high pressure nature of the well, the directional challenges imposed by the high angle in the reservoir, and the metallurgy aspects of operating in a highly corrosive environment. The approach to coping with the high pressures (12,500 psi at 12,500 ft) has been to combine local experience with some of the learning from other parts of the world, notably HPHT drilling in the North Sea. The prediction of a pressure window in which to operate without gains or losses has been generated by analyzing local offset data. The task of staying within that window is crucial to being able to cross open fractures and was aided by utilizing the latest drilling technologies such as Pressure While Drilling (PWD). Directional planning again builds on local knowledge to evaluate different options for achieving the objectives of the well. The latest tools and technologies was required to meet some demanding angle build rates in the lower part of the well in hard rock and through large open fractures. Experience gained in other parts of the world was used as the basis for design since there is no prior application of the technologies in Kuwait. The presence of high concentrations of H2S and CO2 (5,000 – 20,000 ppm & 10,000 ppm respectively) at high pressure has made the metallurgy design a task of finding a way to resolve the conflicts between designing for high pressures, longevity, high levels of H2S and staying at reasonable cost. The final design has achieved a satisfactory balance by using risk assessment to minimize the use of expensive alloys. This was the first well of its kind in Kuwait and could pave the way for the exploitation of a very substantial volume of light crude oil. Management Summary The KOC/BP Drilling Team have successfully completed a 3 year planning and drilling project in the West Minagish 2 (WMN-2), High Angle Well. The WMN-2 Drilling Team achieved an unprecedented well design and construction effort. The well design proved the feasibility of high angle well completions in the deep, Jurassic interval, and set several "firsts" for well construction in Kuwait. Most importantly, the drilling success has opened up the targeting and exploitation of a new reservoir for high quality oil.

For the last 20 years, exploration in Kuwait has focused on finding commercial quantities of high quality oil in the deeper high pressure/high temperature (HTHP) Jurassic formations (13,000–17,000 ft), and for gas within the Triassic formations (17,000–21,000 ft). The HPHT conditions, the presence of H2S and CO2, the narrow pore pressure/fracture pressure (PP/FP) window to work with, and the high mud weights (18–20 ppg) required have made deep drilling conditions in Kuwait some of the most challenging in the world. This paper discusses the outstanding drilling performance achieved in drilling Ruadhatain 206 (RA-206) as the fastest deep Jurassic well to date in North Kuwait. New practices were incorporated and several firsts accomplished through optimum utilization of local built-in experience, combined with the latest technology and practices developed by International Operating Companies (IOC's) and service companies. Optimum bit selection resulted in a world record bit run in the 28" section, and record firsts for Kuwait in the 22" and 16" sections. Careful analysis of offset data and in selecting mud weights resulted in improved hole stability with minimum mud losses, and enabled the bottom two hole sections to be commingled. Extensive cement design and optimization resulted in an excellent CBL being achieved in the production casing. The excellent performance achieved in well RA-206, has now opened the possibility of efficiently drilling similar wells in 100 days (technical limit) instead of the 170–200 days normally taken. (Fig-1) The improved drilling practices significantly reduced the drilling time and well costs, and provided a step-change forward in KOC's understanding of drilling limits when applied to deep exploratory/development wells. Background on Kuwait Geology and Jurassic Well History Most Kuwait development and oil production comes from the shallow Cretaceous formations which extend down to 12,000+ ft, and which have normal pore pressures of less than 12 ppg. These formations consist primarily of sequences of sands, limestones and shales. The massive Burgan field of Kuwait is a good example, where multiple stacked oil zones exist in reservoirs ranging from the Wara formation down to the Minagish Oolite. These shallower formations contain a variety of challenging drilling conditions. The near surface formations are prone to loss circulation throughout Kuwait, with the highest severity of losses in the Tertiary Dammam limestones and the Cretaceous Shuaiba formation, both of which contain vuggy fractures. These formations often experience total losses while drilling, and are commonly penetrated using mudcap drilling techniques. Cretaceous shales in the Ahmadi and Ratawi formations are highly reactive, and require inhibitive muds to prevent hydration and hole sloughing. Hole stability is a concern in the Burgan sand/shales and in the depleted Mauddud formation. Hard and very abrasive sands exist in the Zubair formation, and dense carbonates in the Makhul formation result in slow rates of penetration (ROP's) at the bottom of the Cretaceous. Four casing strings are required to safely isolate the Tertiary and Cretaceous sequences prior to entering the overpressured Jurassic sequences below. With the shallower horizons extensively developed in Kuwait, exploration efforts have focused increasingly on drilling into the deeper Jurassic Najmah/Sargelu and Marrat formations. Penetrating into these Jurassic sediments poses significant additional drilling challenges.

The optimum development of the Deep Carbonate reservoirs in North Kuwait is key to achieve KOC's gas production targets. To optimize (future) production and accessibility of the various Flow Zones within the Target MT formation, KOC has selected a 4.5" mono-bore design to complete the North Kuwait Gas wells. To further improve understanding of production contribution from different flow zones and to enable selective stimulation and effective testing of flow zones, a trial was conducted in a new well to install a 4.5" 15K rated open-hole Multistage Completion (MSC). The well trajectory was designed with all directional work done before the reservoir section. The deviated reservoir section was drilled successfully to the planned TD. A three stage MSC with a long tail string (for future access to deeper reservoirs) was successfully installed. The bottom and middle stages were successfully stimulated and production tested. Stimulation and testing of the upper stage is planned for the future. To build on the success of this first trial another candidate well has been identified and a second 15K MSC system is expected to be installed in the second half of 2017. This paper describes the best practices and the learning in planning and installation of a first successful open-hole MSC in a High Pressure gas well in Kuwait, as well as recommendations for future MSC installations in deep high pressure gas wells with large variations in reservoir caracteristics.

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