Industry Insight: Complete solutions

After a few years in field operations, he spent time in technology staff positions, marketing and line management working within drill stem testing, cementing, well stimulation, coiled tubing and nitrogen services, sand control and other related services. After a period away from Schlumberger working as a consultant, Vorkinn joined Reslink in 2001. Since then and until the acquisition of Reslink by Schlumberger, Vorkinn’s main responsibilities have been within marketing and sales.

O&G. Reslink is a company that has grown faster than industry activity growth over the last few years. What is the reason for this?

PV. Our company has primarily focused on open hole completion technologies within sand control and flow control. Open hole completions have had a solid growth, which we have benefited from.

O&G. What are the driving forces behind this increase in open hole completion activity?

PV. There will be as many answers to this question as there are companies favoring the application of open hole completions. At Reslink, we believe this approach optimizes recoverable reserves in a cost effective manner. The most effective well completion from a cost and productivity point of view is a barefoot completion – without any hardware at all across the productive interval. In most cases this is not a viable option and the second best is open hole with pre-perforated liner, slotted liner or sand screens. We focus on completions with sand screens.

O&G. If this is so efficient, why has this completion philosophy not gained momentum until now?

PV. Again there are many opinions. A lot of people outside our industry as well as within, see the oil and gas industry as very conservative. I believe that this is only part of the reason for the slow evolution into open hole completions. There are also some technical reasons. Many trials with installation of equipment in an uncased, open borehole have failed because the equipment one attempted to place was not robust enough to handle the loads applied in the installation phase. The new generation sand screens have changed this. In the past the screens were fragile – today one can apply tension, compression and torque loads equal to the base pipe the sand screen is manufactured on. A good part of Reslink’s success lies in the robustness of our products and this is key to our internal requirements for all new products. They have to be simple, robust and reliable. Additionally the modern sand screen designs have facilitated delivery of a much higher degree of precision of the filter itself.

O&G. What do you mean by precision of the filter?

PV. The first sand screens used were pieces of tubing or casing with holes drilled in the pipe wall, and with steel wire wrapped around the pipe. The opening between two wires – slot opening – is the opening through which the produced fluid is intended to pass into the production tubing. This slot opening was not overly accurate and, therefore, was not effective in abating the flow of formation particles. We have always tried to design the sand screens with basis in the particle size distribution of the sand in the zone to be completed. The particle sizes tell us how large the screen aperture can be without allowing the formation sand particles to pass through the filter. New computer design systems enhance the accuracy in the screen design process. In order to benefit from improved engineering and screen aperture design, the industry has also been driven towards higher precision of the effective screen opening and verification of the openings. Reslink is measuring every single opening on our wrap on pipe single wire wrap screens. We can therefore verify that the precision of the slot openings is in line with what is required for the optimal sand face completion and filtration efficiency. The precision is also viewed as important by many in order to hold back erosive sand particles, but at the same time allow the finest particles to pass through the system and thereby avoid plugging the screens. In my opinion it is important to avoid screen plugging. If we retain all the particles on the outside of the screen, the flow path for fluids we wish to produce is gradually reduced. The production stops completely or we get flow concentration and eventually we erode holes in the down hole assemblies. In either case, the well is requiring costly repair work or it may well be damaged beyond repair.

O&G. In cased, cemented and perforated wells, zonal isolation control has been very successful. How is this addressed in open hole sand screen completions?

PV. This is another small revolution with swellable elastomers and other open hole zonal isolation systems. The external casing packer has been used for many, many years. They have had a somewhat spotty record. Over the last few years swellable elastomer technology has emerged. These are similar to the traditional external casing packers, just a lot simpler. In principle they are a rubber sleeve outside a standard casing pup joint. The rubber compounds are designed to swell and isolate sections in open hole when exposed to produced fluids. There are also operators who let mother earth handle the zonal isolation and annular flow issues, simply by letting the formation collapse around the sand screen. This approach used to worry us in the past when the sand screens could not handle any collapse forces.

O&G. What are the main characteristics of the open hole well and where do you see this technology moving from here?

PV. The wells are drilled longer and longer – most of them horizontal to penetrate as much productive interval as possible. Long sections are challenging us in so far as securing contribution from the toe to the heel. One technology that is taking off is flow control devices for these wells. These devices are intended to ensure that the entire horizontal section that one has spent lots of money drilling, actually produces. The simple form of these flow control devices are housings installed on sand screens. The sand screen does not have all the holes drilled along the entire joint, the fluid passing through the sand filter is flowing along the external, un-drilled pipe wall into the flow control device housing. The housings are designed to even out the flow contribution from toe to heel. I think that the vast majority of open hole completions will have some sort of flow control devices installed as a ‘standard’ within very few years. It makes sense from a cash flow point of view and even more so when considering NPV for a well or field.