Turning Water into Oil

However, with the aid of technology, determining, analyzing and acting inside, the well bore becomes a possibility that allows for on-the-spot trouble-shooting. Welltec® has developed a series of technology that efficiently manages produced water from reservoirs.

Oil production and well management is a continual exercise in improving the yield of the system and to evaluate the potential of initiating measures that can increase this. One measure is the management of produced water that has complicated oil production repeatedly, and sometimes even made it non-profitable. A proven method for managing water is tractoring, especially in horizontal wells, where conventional intervention methods have difficulties progressing.

Scope of the Challenge

It is estimated that 250 million barrels of water is produced worldwide each day. Water-to-oil ratio increases over the life of a well, which means that mature wells produce approx. 9.5 barrels of water for each barrel of oil. Without a doubt, this is not very cost-effective for the operator. In Norway, some wells produce up to almost 100% water, causing operators to abandon wells before even initiating inhibiting measures. As produced water is an inextricable part of the oil recovery process, it is imperative to develop and apply the right technology to separate water from crude. Welltec® has developed a series of down hole mechanical services offering clear cut intervention performance and keyhole precision in water management.

A New Solution to Water Management

Welltec’s solution is based on Well Tractor® technology, which offers the possibility to deliver new services, both when it comes to detection as well as alleviating water influx problems. This is due to the fact that the Well Tractor® is an efficient means to convey logging instruments into the well bore for analysis of the well characteristics along the horizontal section of the well bore. The subsequent analysis allows engineers to design and implement innovative solutions that maintain or increase the production while e.g. reducing influx of water.

As every well is unique, solutions need to be unique as well. Part of this includes having a flexible solution that allows for making adjustments during operations. New solutions need to focus on increased flexibility in well management to address challenges of immediate trouble-shooting. Having a flexible completion structure allows for current optimization and Welltec® offers that with the Well Tractor®.

Advantages

A unique feature of the Well Tractor® Technology is that it is surface controlled, thus eliminating the need for an expensive rig. An additional benefit of being surface controlled is the fact that this also eliminates the need for mobilizing heavy equipment, which means engaging a smaller number of personnel and reduced operational hazards. Furthermore, the required equipment is logistically easier to handle and the rig-up time is reduced considerably compared to competitive technologies. With a solution running on electrical wireline, the door also opened for accessing even highly deviated wells. The Well Tractor® provides operators with reduced personnel requirements, quick mobilization to and from site, easy handling on site and down hole conveyance speed far surpassing other technologies. Very importantly, the services offer unseen versatility and water cut decreasing from 85% to 5% as outlined in the case histories below. Additional benefits are 50% cost-savings, wells quickly back on increased production and also exposed to fewer risks.

World’s first Setting of Bridge Plug under X-flow

The Well Stroker® has been used successfully as an anchor to set a bridge plug at 10,384 ft in 300 Sm3/D X-flow with a pressure of approximately 30 bar differential in 5” liner. The operation took place in the North Sea in July 2006.

Based on production logging tool results from 2005, the operator decided to isolate a zone with high X-flow. Due to risk of plug movement, the bridge plug was anchored by the 318 Well Stroker® D-type. Though the Well Stroker® is capable of applying an axially focused force of up to 33,000 lbs, the anchoring force was limited to 15,500 lbs in order to allow upwards movement of the running tool. This was done to shear free from the plug during the setting sequence.

After setting the plug, the Well Tractor® successfully installed a 23 ft straddle across 9,990 – 10,013 ft in one run to isolate a 10 ft water-producing interval. The first well test data after the water shut off indicated that the water rate was reduced from 2,150 to 150 m3/sd. The oil rate was maintained at approximately 200 Sm3/D, and the water cut was reduced from 90% to 45%.

The last two years, produced water handling capacity had restricted the field and the pressure support in the closed-off zones had been insufficient. The result of the Well Tractor® job is thus expected to improve the total oil production at field level. As an additional benefit, the operation is also expected to reduce the environmental impact.

The job could not have been done without the Well Tractor® and Well Stroker® as other tools did not have the necessary force combined with precision to set the plug in the high X-flow.

Isolating Sliding Side Door

Another well in the North Sea producing since 1995 was isolated with tubing including 2 sliding side doors (SSD) to control production. Attempts had been made to close both SSDs in 2003, but only the upper SSD had managed to close. A two-piece straddle was sat above the lower SSD, which however did not change production. A PLT test showed there was an internal leakage in tubing. In 2006, the straddle was retrieved and the well temporarily plugged.

Eager to get production flowing, the operator decided to apply Well Tractor® Technology. The Well Tractor® and Well Stroker® were used to isolate lower sliding side door with a 72 ft long straddle and to isolate hole in tubing above lower straddle with 26 ft straddle. The results of the job were impressive. Water cut was reduced from 85% to 5%, gas to oil ratio was decreased from 2000 to 200, and Q oil was boosted from 100 to 900 Sm3/d.

Future Perspectives

Implementation of novel solutions is the true essence of Well Tractor® Technology and there is still enormous potential to unlock. In the future, Welltec® will continue to develop the series of down hole mechanical services in order to further improve existing water managing services.