High-tech wells provide new options for overcoming many of the difficulties in recovering oil and gas from the varied and heterogeneous reservoirs often found today. Either separately or in combination, technologies such as multilaterals, intelligent wells, and expandable tubulars allow for the exploitation of reserves that previously might have had to be left in the ground.
This week's PennWell High-Tech Wells conference and multilateral short course, in Galveston, Tex., Feb. 10-13, highlight many recent field experiences with these technologies.
In addition, this week's issue of OGJ features a special report on multilaterals, beginning on p. 39, that discusses how the industry group TAML (Technical Advancement of Multilaterals) aims to disseminate information about the benefits of multilateral technology, so that multilaterals move more toward the forefront in well-design decisions.
Finding acceptance
One problem the oil and gas industry faces is the relatively long time for new technologies to be widely accepted.
For instance, the first modern multilaterals date back to the early 1990s, the first intelligent well field trials were in 1997, and work on expandable pipe also started in the 1990s.
To date, the number of wells featuring these technologies is still few when compared to the more than 1 million wells on production in the world.
Although estimates vary, some ball-park numbers provided by Carlos A. Glandt, global implementation manager, smart well solutions, for Shell International Exploration & Production BV, indicate how many wells include these technologies.
For instance, regarding multilaterals, his numbers show that the industry has installed at least 1,200 Level 1, 700 Level 2, 290 Level 3, 228 Level 4, 48 Level 5, and 15 Level 6 multilateral completions. This issue's special report on multilaterals also contains definitions for the TAML levels.
As for intelligent wells, Glandt says that there are at least 152 wells with downhole flow control. Of these, about 87% are offshore, either in wells completed from a platform or subsea.
He also says that there have been at least 150 expandable solid-pipe jobs (100,000 ft of pipe) and 150 expandable-screen jobs (150,000 ft of screen).
Glandt cautions that his numbers are for pointing out the level of maturity of a particular application, and so some may not be totally accurate.
Increasing options
Drilling and completion systems have grown in complexity over time. In the past, the industry drilled most wells as vertically as possibly, although some wells had sloping trajectories, especially those drilled from offshore platforms. These deviated wells often had an S shape that resulted in a vertical wellbore through the reservoir.
The late 1980s saw the growth of horizontal drilling that further added more choices for the type of well to drill and complete. Also, geosteering drilling tools became available that made it possible to drill complex designer trajectories or extended-reach wells that allowed more options for reservoir development, especially in the high-cost offshore environment.
Multilaterals have added another dimension to well design. Although multilaterals often can be associated with horizontal laterals, the geometry of the legs drilled from these wells may vary and include complex designer-type trajectories.
These wells can cost more, but one multilateral may cost less than the two or more wells with other geometry that would have been needed to obtain the same results.
Multilateral wells have advantages such as increasing reservoir exposure, thus increasing the production rate; improving reservoir drainage caused by reservoir heterogeneities; delaying water or gas coning; connecting fractures; and reducing slots needed on an offshore platform or subsea template.
Another benefit is that multilaterals allow immediate production from secondary reservoirs in a well. Production from these zones, except when completed with multiple tubing strings, often had to wait until the primary zone was depleted.
Intelligent tools and expandables further enhance multilaterals and other well geometries. Intelligent completions provide a means for monitoring and controlling from the surface the production from each multilateral leg or each zone in a monobore well, while expandable tubulars provide larger wellbore diameters that are often needed for producing complex reservoirs.
In general to date, these technology advancements have provided well- design solutions for a number of niche applications. But as knowledge grows, this high-tech future may become the norm.
