Production optimization has become a buzz word within the industry as operators ask, "How can I get more from what I have already got?"

After many years in the doldrums, interest in well intervention is increasing rapidly in line with commodity prices. The relative shortage of greenfield opportunities is leading operators to refocus on their brownfield assets. Investments that improve overall recovery factors and extend economic life for existing assets can have spectacular returns on investment.
The cycling of assets from majors to independents is further increasing interest in well intervention as new owners look to boost production from these brownfield sites. The smaller companies can be more nimble than their larger cousins and therefore can more easily identify and implement incremental production improvements. Well intervention is the quickest and lowest risk method to achieve this.
Changes in asset ownership also bring up another issue. How many of us would buy a house without doing a survey or buy a car without opening the hood? Yet many asset acquisition decisions are based on incomplete or patchy well information files and the knowledge possessed by personnel most familiar with the asset is often lost as they change positions or companies.
Where good records are available, questions are raised such as: how much incremental production could be achieved by re-perforating, completing bypassed zones, water shut-off, leak prevention, scale and wax removal, etc.? At the most basic level, how many wells around the world are shut-in today for unknown reasons? With oil at US $20/bbl there may have been limited interest in determining why, but at $60/bbl the picture changes.
The increasing level of well intervention activity shows that the industry has started to address these issues. After a long period of under-investment within the service industry, focus is back on capital investment plus recruitment and training of personnel in order to meet these rising activity levels.
Meeting the requirements of these increased activity levels is not the only issue for the service industry. While high commodity prices can mask the issue, technology and knowledge have a major role to play in improving cost-effectiveness and delivering improved overall hydrocarbon recovery factors. Enabling technology for deepwater developments has been a key focus for the industry over the last 10 years, with brownfield intervention technology a poor relation. However in today's more positive environment, brownfield intervention technology represents, in many cases, a quick win.
Areas such as perforating which had been commoditized over recent years, are now becoming current subjects for consideration again, with new investment and interest. Coiled tubing is another area that has moved from being a commodity to a technology hot spot with through-tubing rotary drilling (TTRD) applications.
Thinking outside the box
Technology for brownfield well intervention has lacked investment and focus for some time, so it is useful to look outside the industry to see what new ideas have evolved, and to review their potential application in oilfield operations. Two such technologies which have revolutionized life outside the oil industry are digital cameras and wireless.
Downhole Video. Cameras and video technology are already at the forefront of almost every technology area from medicine to space. Now we are beginning to see reliable application in the downhole oil and gas sector.
While not a brand new technology development, the use of downhole cameras is rapidly gaining acceptance as a cost-effective means of "seeing" what is going on in a well. Identifying dropped objects and fishing was the original application for cameras but today they are used far more often for mechanical inspection and fluid identification. Being able to see what is happening in the wells rather than inferring or assuming can prevent expensive mistakes.
Case 1. For example in the Gulf of Mexico, production from a relatively new gas well was beginning to drop off significantly. The well was flowing up 51?2-in. casing and was believed to be "loading up" with condensed water as slugs of low chloride water were periodically being unloaded. With production at a depth of 13,400 ft (4,085 m), the operator wanted to use a downhole camera to identify the point at which condensation was occurring. Then a velocity string would be run to this depth in order to minimize friction and reduce installation costs. The camera would be used to identify the depth at which "wet gas" would become dry.
Figure 1 shows the money shot from the camera run. Instead of the expected condensation problem, a significant amount of scale was found to be covering most of the perforations. The rapid decline in production was caused by scale choking off production rather than fluid loading. Instead of running a velocity string, the operator mobilized a coiled tubing unit!
Case 2. A live video was used for fluid identification in a well in the US Rocky Mountains. The full motion video survey showed gas and water entering from the perforations. It revealed that only a few perforations were producing.
Below the fluid entry, gas and water appeared to be sucked into a thief zone. Analyzing this with a standard production log or even a multi-arm, distributed sensor tool would cause some head-scratching. Seeing production from individual perforations is a novel experience for those who have not been involved in well engineering.
The next stage of camera technology development will be to integrate traditional tools such as calipers and production logging tools with video, so that an operator can get both measurements and pictures in the same run in the hole at an incremental cost. This enhancement is expected to become available within the next twelve months.
Wireless Technology. In a similar way, "wireless" technology is an integral part of our lives in applications from cell phones to laptops. The technology has progressed immensely over the last 10 years and like cameras and videos, downhole wireless applications are now beginning to gain acceptance in the oilfield.
In a production environment, well intervention requires entry into the well with either wire or coil tubing. Intelligent completions or smart well technology was developed to reduce or minimize the need for these interventions. While the take up of smart wells has been slower than originally anticipated, minimizing well interventions has benefits in certain circumstances. Wireless in-well transmission of data has the potential to achieve to solve this problem. Transmissions have now been achieved from 12,000 ft (3,659 m) to surface with no repeaters, albeit in optimal conditions.
In-well wireless transmission is being used for niche reservoir monitoring applications where data cannot be cost-effectively obtained by traditional methods. For example wireless gauges are being installed in a subsea well in the North Sea.
Traditionally when an appraisal well is drilled offshore, at the end of logging or testing, the well is abandoned and no further data obtained. For limited additional cost, a wireless pressure gauge can be installed at the reservoir depth with a plug set above it. The well is then abandoned as normal. A recorder box with an acoustic transmission system is installed on the seabed. The subsea system then records pressure and temperature measurements from the downhole tool. As and when required, a vessel can come by, drop a probe over the side and recover the data from the subsea recorder (Figure 2).
The reservoir data thus obtained can be used for interference analysis with nearby producers/well tests or even long term build-up. The same approach can be used for vertical interference tests within the same well.
While wireless transmission is today used for data, control applications are not far away. Transmitting from surface to downhole has the major advantage that there is typically an infinite power supply at surface and transmissions can therefore be made in "continuous mode," allowing wireless systems to be used in applications such as replacing failed safety valves. At present storm chokes are used in this application but they have inherent problems. A wireless valve to replace storm chokes is the first stage in the development of a portfolio of downhole wireless valves. The retro-fit "intelligent well" which can be deployed as needed moves the operator's expense from capital expenditures to operative expenditures, removes the long-term reliability concerns and eliminates the need to attempt reservoir performance projections years into the future.
Conclusion
Without doubt there are other technologies and ideas that can be brought into the oil industry from outside. The use of composites in the aerospace industry has progressed hugely over the last decade, but applications within well intervention are very limited. The size and capability of electronics has changed out of all recognition, but oilfield downhole instrumentation has remained virtually the same size.
With renewed focus on production optimization and hence on well intervention, the industry must continue to look outside its own boundaries and apply proven technologies from elsewhere, in innovative ways, to provide cost-effective solutions.

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