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Mature wells—what are we to do with them?
They've been there a long time, maybe so long that people look
right past them as they look for the next prize. Fortunately
for those with patience and ingenuity that are willing to
"smartly" work hard, there is still lots of cash in "them thar
hills." Hart's recent Brownfields: Optimizing Mature Assets (BOMA)
Conference (Sept. 19–20, 2005 in Denver) was all about
intelligently working those hills to wrestle more of the
buried oil and gas treasure from them. Capturing insights from
this conference for this article naturally led PTTC to point
people toward information/insights from other sources.
In addressing conference attendees, Bill
Pike with Hart E&P noted two key points: (1) oil and natural
gas dominate the primary energy production today, and will
continue to do so in the foreseeable future, and (2) the oil
and gas supplied from new fields will decrease from 50–60 % in
1960 and 15–18 % today to 7–10 % ten years in the future,
making it very important to optimize the mature field
production. There will be many wells to optimize—at the start
of 2004 in the U.S., there were about 393,000 marginal oil
wells and 260,000 marginal gas wells, according to a recent
study performed by DOE's National Energy Technology Laboratory
(SPE 98014). These wells produce 28% of oil production and 11%
of gas production. Moving forward to 2025, this contribution
will increase to 32% of oil and 17% of gas. The number of
marginal oil wells will decline while the number of marginal
gas wells will increase significantly, with much of that
growth occurring in the Rocky Mountain region.
Industry presentations during the conference
had a strong focus on natural gas production and related
technologies. There are often several required in combination
that will remove/cause less damage or solve operational
problems. There is some natural spin-off appropriate for
marginal oil wells. Some key insights from different
presenters include:
- There must be a proactive, integrated
approach to production enhancement. This approach identifies
opportunities as opposed to reacting to problems, high
grades those opportunities and applies the solution in
groups. It is project-based and focuses on cost effective
applications proportional to the asset value and projected
upside. (Mark Brinsden, Expro Group)
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- To augment the resources of local asset
teams for dealing with mature fields, Chevron has created
two new technology work teams—Formation Productivity and
Production Engineering. Further, they will form small teams
of production engineering experts to go "on location" to
work with the asset teams to analyze and remediate
production and injection problems. Expertise within these
teams includes, among others: lift optimization, wellbore
nodal analysis, screening inactive wells for sand and water
cut improvement, and stimulation expertise. (Brian Llewelyn,
Chevron Energy Technology Company).
- As he discussed gas well liquid loading
issues, George King with BP stressed that mature field
optimization must be much more than an "office" exercise,
reinforcing the "on location" concept that Chevron employs.
The people "on the ground," the field records, and visual
inspection/observation all provide essential clues that are
relevant.
Water Management
Gas Wells. With maturing gas wells, liquid loading can
be a dominant problem. George King with BP noted how critical
it is for operators to:
- Analyze well behavior and detect liquid
loading,
- Understand water sources and identify the
source of the problem,
- Calculate the critical velocity to remove
liquids, and
- Among the several technologies available
for liquid loading, choose one that matches the problem
(i.e., screening criteria). Note that in this realm there
may not be one "best" technology—several may work and there
is a certain amount of "try it and see" when deliquifying
gas wells.
Both King and John Misselbrook (BJ Services)
discussed the technology choices available today, along with
their advantages and disadvantages. James Lea at Texas Tech
University also has recognized expertise. Readers are referred
to an article published in SPE's Journal of Petroleum
Technology (April 2004, p. 30+), which PTTC summarized in a
past newsletter available online at
www.pttc.org/news/2qtr2004/
v10n2p4.htm. Beyond general insights, Lea's
article lists 23 references, many of which are SPE papers
presenting field results.
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Those wanting to learn more should consider
participating in the Annual Gas Well Deliquification
Conference organized by the Artificial Lift Research and
Development Council (www.alrdc.
com) and Texas Tech's
Southwest Petroleum Short Course which is held each spring in
Denver. Some field results presented in the 2005 Conference
are summarized in PTTC's Tech Connections column in the April
2005 issue of The American Oil & Gas Reporter (www.
pttc.org/columns/aogrcoapr05.htm).
These typify what one can expect by attending the conference.
Through the years PTTC has published several
relevant case studies in its Petroleum Technology Digest in
World Oil (www.pttc.org/
case_studies/case_studies.htm),
covering an automated soapstick launcher (Sept. 2002),
capillary strings (Feb 2003) and a 2-piece flow-through
plunger (Aug 2003). PTTC also devoted the State-of-the-Art
article in Network News in spring 2003 (www.pttc.org/news/
1qtr2003/v9n1p7.htm) to
gas well deliquification issues.
John Misselbrook with BJ Services described
one of their new technologies, the AquaLift jet pump. Using
concentric installed coiled tubing, it creates three conduits:
one for gas production, one for liquid production and one for
pump power. The pump is on the surface, so there are no moving
parts at the bottom of the well, which increases its
reliability. It is a good alternative where the pressure is
depleted but has good produceability, particularly
intermediate depth gas wells making a moderate amount of
water. An example was presented of an 8,000 ft. well producing
200 Mcf and 40 Bbls of water per day through 2 3/8-in. tubing.
If the well is choked by 25%, it loads up and dies. The result
of installing a velocity string is compared with the AquaLift
option. With only 13 hp, the jet pump delivers the 40 Bbl/day
of water and dry gas to the surface while the 1 3/4-in.
velocity string works but only until a modest reduction in
bottomhole pressure occurs.
Oil Wells.
Excessive water production is not just a "gas well" problem.
Some time ago PTTC devoted resources to capturing "common
sense" knowledge about managing water production into a
concise handbook available through its website (www.pttc.org/
pwm/produced_water.htm).
Production chemicals are another of those "every day"
operational things that it behooves operators to devote some
attention to. BJ Chemical Services spent some time during the
conference discussing the current economics of chemical
remedial services in tubulars, near wellbore and reservoir and
discussed specific treatments for the problems cited.
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State-of-the-Art
Summary