Horizontal wells have dominated conventional wells because of their
increased production rates, improved recovery efficiency, increased reservoir
drainage area, and delayed gas and water coning. However, nonuniform-flow
profiles can result in premature water/gas production, loss of production and
reserves, and a decrease in profitability, which will shorten the life, and
defeat the purpose, of a horizontal well.
This paper describes a new production-technology system that will optimize
production, delay water/gas coning, eliminate/minimize annular flow, and ensure
uniform inflow along the lateral at the cost of a minute pressure drop in long,
high-rate horizontal wells. A case history is presented in which this
production technology, combined with sand-control technology, has resulted in
significant savings for the operator and improved production in offshore
horizontal oil wells.
A mature clastic reservoir was drilled offshore Saudi Arabia. The Z-field
was put into production in 1972, with 220 wells drilled to date. The majority
of these wells are vertical wells targeting the 3.5-darcy high-permeability
massive sands in the principal reservoir of the field.
Recently, to increase oil production, the development and drilling
strategies on an eight-well platform were switched to drill horizontal wells in
all but one well—the platform locator (see Fig. 1). Six of the horizontal wells
were completed with an average of 3,400 ft of cemented 7-in. liner. Only the
best-quality pay (25 to 40% of the horizontal section) was perforated by use of
costly 3⅜-in. tubing-conveyed perforation (TCP) guns.
In addition to the rig time and high cost involved in this type of
completion technique, high risk is also taken by having the TCP guns on rig
location, because it raises a number of safety concerns.
A new production-completion system was being evaluated in the last
horizontal well (Z-253) in the same platform. The evaluation results of this
new production-completion system showed a minimum potential saving of U.S.
$240,000, with three rig-days ahead of the drilling schedule, by eliminating
running, cementing, cleaning, and perforating of the 7-in. liner. The decision
was finally made to run the safer and more cost-effective 2,200-ft new
production-completion system to meet the main objective of extending the life
of the horizontal Z-253 well.
© 2005. Society of Petroleum Engineers
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- Original manuscript received:
17 August 2003
- Revised manuscript received:
25 May 2004
- Manuscript approved:
10 June 2005
- Version of record:
15 September 2005