Forty nine high rate oil wells were completed with gravel packs in Maxus' Intan/Widuri fields in a nine month period. packs in Maxus' Intan/Widuri fields in a nine month period. Lower than expected productivity on the initial completions resulted in an extensive investigative test program conducted primarily at the field level. The test program, the procedures used and the results of these tests are reviewed. The procedures used and the results of these tests are reviewed. The investigations include fluid and gel compatibility with the formation, determination of the critical gravel pack slurry parameters, pressure losses across different screen types, parameters, pressure losses across different screen types, and the outcome of various gravel placement techniques.
The primary conclusions are as follows. Slurry gel viscosity was the most critical parameter in the amount of gravel placement. Perforation washing in conjunction with placement. Perforation washing in conjunction with underbalanced tubing conveyed perforating (TCP) gave significantly better gravel placement and productivity than only underbalanced TCP. The use of a short cleanup test following completion is beneficial in early identification of a production impairment.
The Intan, Widuri, and Northeast Intan fields are located 90 miles [145 kms] north of Jakarta, Indonesia in the Java Sea. The discovery wells were drilled in October 1987 and April 1988 with the primary field development and completion operations occurring from March 1990 to February 1991. The reservoirs are immature fluvial or distributary channel sandstones within the late Oligocene - early Miocene Talang Akar Formation at approximately -3200' to -3700' subsea.
The decision to gravel pack was made for the following reasons:
* High production rates were anticipated based on drillstem test (DST) results on the discovery wells. Theoil has a viscosity ratio to water of 12:1 - 14:1 at reservoir conditions. * The primary drive mechanism was expected to be awater drive. Large volumes of water will have to beproduced to recover all the oil reserves. * Water production or two phase flow often causessand production. * The artificial lift method is electrical submersible pumps (ESP's). The run life of an ESP can beseverely reduced with sand production. * Core work indicated little to no cementation makingsand production likely under the above conditions.
PRELIMINARY WORK PRELIMINARY WORK Core work showed the reservoirs to be predominantly quartz with approximately 5 - 6% clays. The clays were analyzed as 85% to 95% kaolinite with occasional smectite, chlorite, illite, or feldspar interdispersed. Sieve analysis identified a gravel size of either 12–20 or 20–40 mesh gravel based on Saucier's criteria. Return permeability tests to various completion fluids showed 94% - 100% regained permeability except on distilled water. Thin sections and permeability except on distilled water. Thin sections and scanning electron microscope (SEM) work showed little to no cementation in the majority of the sands with the cores being held together by a high pour point crude.
The crude is a high pour point crude with a 32 API gravity. Analysis of the crude showed a low asphaltene content of 0.15% to 0.3% and emulsion tests were run on all the acids prior to use. Later crude analysis using gas chromatography prior to use. Later crude analysis using gas chromatography would reveal an asphaltene content of 5% to 7%. The crude viscosity at reservoir conditions is 4 - 4.2 centipoise.