Page 45: of Offshore Engineer Magazine (Feb/Mar 2014)

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Pipelines spews from the bottle. Result: no change in production. At the pump effectiveness and lifetime (Figs. production operations. Much of the

The surface-installed electromagnetic end of the two-week period the choke 2-3). The water injection system uses mitigation effort has been centered on technology does not alter the thermody- setting was changed to that where the polyethylene piping for the distribution chemically inhibiting its formation or by namic state of the system or its evolution, maximum CaCO deposition had been headers to electric submersible pumps mechanically removing it. But the steps 3 as with chemical treatments. Instead, it observed. The well continued to oper- (ESP). The mineral content of the waters are often unsatisfactory. controls where and how that thermody- ate at high effciency and production in the distribution system is very concen- A new approach to the problem is namic evolution occurs by transmitting levels indicate no scale deposits after 10 trated and thus the water conductivity is focused on preventing the deposition an electromagnetic feld that interacts months of steady operation. high. of scale rather than treating it when it with the ions present in the aqueous ClearWELL was applied to control car- This circumstance allows the aqueous appears. The success of this system in solution to generate nucleation sites. bonate scale in wells offshore Africa. In medium to serve as both the antenna and global applications suggests a major step

ClearWELL works as a threshold nucle- this instance well operation was plagued transmission line for the electromagnetic forward in production operations.

ation device. by scale build-up, which restricted and signal. The impedance of the transmis- Mineral deposits had reduced pump

The technology uses a magnetic loop eventually blocked oil production. The sion line is much higher per linear foot effectiveness and lifetime in a reinjec- antenna to induce a radio frequency operator wanted a method to control than those seen in metal piping schemes. tion system. No deposits occurred after signal in the metallic piping and aqueous scale as determined by bottomhole pres- This limits the propagation of the sig- installation of the ClearWELL system: conductive path provided by the water sure without acid treatment or installa- nal. To partially account for this, two (A) shows the pump condition at startup; system. The conductive medium acts tion of capillary tubing for continuous ClearWELL units were installed—one on and (B) shows it after three weeks. both as an antenna and as a transmission injection of scale inhibiting chemicals. the water input and one on the output line for the current. Fig. 1 shows a graph of bottomhole distribution header. Alasdair Macneil Fergusson is the

There are several advantages to pressure as determined during a trial The units were placed on the system Director of engineered chemistry for introducing an interaction that moves period and prior to the trial. BHP steadily after one day of operation. In a 34-day Weatherford Oil Tool Middle East Ltd., throughout the system. By delocalizing, increased prior to the ClearWELL pro- observation period, the installation saw based in United Arab Emirates. He has the system can be installed and applied gram and has remained near-constant no net deposit formation, and depos- a degree in Chemistry from University of without detailed knowledge of the loca- since its introduction. its that had formed in the unit prior Aberdeen. tion where conditions exist for the forma- The technology can also be applied to installation were cleaned up by the tion of mineral deposits. Because the onshore. In the Ketchum Mountain system (Fig. 4). Wiley Parker is a Technical Specialist current moves throughout the system, the area of West Texas, water from several in Weatherford’s Business Development

A major solution device can be surface-mounted, without sources is sent to a pumping system for division, based in Houston. He earned a intrusion into the wellbore. reinjection. Mineral content of the waters Scale is arguably one of the most dif- PhD in Chemical Physics from Washing- produces signifcant BaSO that reduces fcult and expensive problems facing ton State University.

4

Application examples

Offshore scale control is a complicated endeavor. There are logistical issues associated with timely chemical deliv- ery as well as environmental concerns

ONSHORE. OFFSHORE. associated with any chemical residues which may be released into the environ- ment. Environmental concerns have

EVERY SHORE.

been especially problematic in North Sea applications. ClearWELL has been tested

Certi? cation | Training | Events | Standards | Statistics | Safety by an international operator off Denmark

Washington, D.C. | Houston | Beijing | Singapore | Dubai | Rio de Janeiro in the North Sea, on a platform well 877.562.5187 (Toll-free U.S. & Canada) | +1.202.682.8041 (Local & International) | [email protected] | www.api.org with a dry tree producing from a chalk reservoir. Treated seawater was used for reservoir pressure support. Historical operation of the well resulted in severe calcium carbonate deposition through- out wellbore and surface equipment.

Chemical control is impractical and the deposit problem has been historically managed by reducing the choke setting to minimize pressure drop. This severely impacts the rate at which oil can be produced. Even with the reduced choke setting, acid treatments were required on a nine-month schedule to maintain production. Historical data showed that ® at full choke well scale up occurred in

It’s a tough business. Look to API.

approximately two weeks.

ClearWELL-R was installed in March

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2013. Production strategy was to main- tain original choke setting for two weeks.

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