Drilling in Uvat is unique: wells with similar parameters are drilled nowhere else in West Siberia. Here directional, horizontal and dual completion wells are drilled and experts say that implementation of innovative drilling solutions was among the factors that have made Uvat full-field development cost efficient.
In developing its Uvat project, TNK-BP decided to rely on the socalled ‘super well pads’ with 48 wells per pad rather than conventional well pads designed for eight to twelve wells. One such super pad produces the same amount of oil as four conventional well pads put together.
The decision was driven, first and foremost, by the inaccessibility of Urna and Ust-Teguss fields. All equipment and materials for both drilling and well pad construction (geofabric, slabs, sand, gravel chippings) have to be delivered to the fields while winter roads are operable, i.e. during three months per year only. In addition, the implementation of the unconventional field development option simplified production and transportation infrastructure and reduced associated costs. Finally, developing the same amount of reserves with fewer pads translated into reduced environmental risks.
Idea Comes True
On the other hand, drilling of a large number of wells from a single well pad is restricted by the technical capacity of drilling rigs and tools. To cover the entire field area, it was decided to drill extended-reach wells and to do so advanced heavy-lift rigs were needed.
Back in 2006, when the mobilization of equipment and materials to be shipped to Uvat was started, TNK-BP purchased four Germanmade Bentec rigs and the fifth rig will be delivered to Ust-Teguss in the winter of 2011. All five are 320-ton train top-drive rigs with diesel power generators and are fully operable in arctic conditions. On one super pad two rigs can work simultaneously moving from well to well on skid beams. This solution has saved costs for move in rig up. Drilling of all wells in one super pad takes up to 18 months on average. With this state-of-the-art equipment in place, it became possible to drill S-shaped directional wells with a 3,000-meter step-out and more (the record step-out is 3,506 m) in a rather shallow pay horizon occurring at 2,450 m (well measured depth (MD) reaches 4,500 m; hole drift angle is up to 60о).
To further improve the development efficiency of the main production target, Yu2 reservoir, it was decided to drill horizontal wells with horizontal sections of up to 800 m (MD is 4,600 m; step-out is 3,520 m).
Six wells of that kind have been drilled thus far; four of them have been put on stream with an average flow rate of 310 tpd. In 2011, horizontal drilling will be piloted in Yu4 reservoir as well. Apart from that, specialists are looking at the cost efficiency of multilateral drilling to develop either one target (Yu2) or both Yu2 and Yu4 to organize dual production or dual injection. When implemented, this solution will reduce the scope of drilling as well as provide better reserves drainage efficiency and higher flow rates as compared to the multi-layered reservoir development option that relies on wells drilled to each of the reservoirs individually.
KCA Deutag from Germany has been the drilling contractor since the very beginning of drilling in Urna and Ust-Teguss back in 2007. The drill crews working in Uvat include mostly Russian drillers, whereas expats occupy the positions of tool pushers, senior mechanics and other key positions. International specialists work in the drill crews to share their expertise and skills, and so the expat staff is gradually replaced by Russian personnel.
Halliburton is the service contractor in directional drilling, measurement while drilling, drill muds, bits and cementing. TNK-Uvat intends to engage yet another service contractor to work, in particular, in Tyamkinskoye field in Uvat Central Hub. Yet the remoteness of Uvat fields once again constrains the implementation of this initiative. Thus, Halliburton delivers about 10 t of materials and chemicals to Uvat every year and their delivery should be over in the three winter months. Yet prior to actual delivery to the fields all the materials need to be gathered at one of consolidation hubs (Turtas or Nizhnevartovsk) and since many chemicals are imported from abroad, their delivery to consolidation hubs only may take weeks if not months. Therefore, any contractor, having won a tender, would need enough time to purchase and deliver its materials before the start of the winter delivery campaign, which means that the tender timeframes become a crucial factor.
Nonetheless, TNK-Uvat is quite determined: new service contractors will bring their know-how technologies to Uvat and, moreover, effective competition among the contractors will definitely improve the quality of their services.
Striving for Performance
Back in 2007, in the early days of drilling in Uvat, TNK-Uvat Drilling Dept. had only four employees while today it has 45 specialists (including supervisors). Their key objective is consistent improvement of the drilling performance. It took 37 days to drill the first well in Urna while three years since a similar well can be drilled in mere 15 days to 16 days, and the well construction record is 12 days!
One of the key factors influencing the drilling performance is the drilling contractor efficiency. That is why Uvat followed the example set by other TNK-BP fields and introduced a drill crew incentive program that provides bonuses to the crews that have managed to drill a well ahead of plan (number of days to drill 1,000 m is considered) while ensuring high work quality and adhering to HSE standards.
Another way to boost performance is to apply the tools proposed within the Technical Limit project that was launched in March 2010. The concept is to introduce and/or improve work methods and processes and establish new leadership skills in drilling managers, line managers and contractors working on site (see “A Journey from Good to Better to Best: TNK-BP Drilling Introduces a Technical Limit Approach in Orenburg and Uvat”, Innovator # 36).
The consistent effort to improve drilling performance has resulted in an outstanding accomplishment: on September 8, 2010, it took a mere day to drill 1,000 m with KCA Deutag’s T501 rig in Well #2500 of Ust-Teguss. Before that the daily penetration rates had had three digits only!
Lower costs and accelerated production are the cornerstones of consistent and dynamic progress of any oil and gas company. This is particularly true for strategic projects, such as TNK-BP’s Uvat, and the drilling successes in Urna, Ust-Teguss and Tyamkinskoye undoubtedly generate extra value for the Company.