A History of Sand Control in the Teak Field
Authors: Likwartz D.J. 
Published: December 2007

In the Teak field, extensive testing over a 3 1/2-year period has resulted in techniques that keep sand production to a trace while allowing the wells to be produced at rates exceeding 5,000 BOPD. As of March 1975, these sand-control methods have enabled production of 44 million bbl of oil from eight unconsolidated sand horizons.

Introduction

Amoco Trinidad Oil Co. discovered the Teak field, located 25 miles off the east coast of Trinidad (see Fig. 1), in Sept. 1968, and production began from four wells on the Teak A platform in Jan. 1972. As of March 1, 1975, 34 wells had been drilled from three platforms to develop the field. Some type of sand control had been installed in 28 of these wells. Amoco Trinidad has two other oil fields on production - Samoan and Poui - but neither has experienced any significant sand problems. problems. The Teak field is a highly faulted anticlinal structure containing 40 productive fault blocks. The sands and shales in this north-south trending anticline were deposited by the Orinoco River in Venezuela. The Teak field contains 14 oil-productive horizons of Pliocene and Miocene age found at depths ranging from 4,200 to 12,200 ft. The shallowest eight horizons are unconsolidated sands requiring sand control. Starting with the shallowest horizon, these sands are named T, T-1, U, MM-0/1, MM-0/2, MM-1/2, MM-2, and MM-4; the first three of these have the most severe sand problems.

The sands are among the finest grained discovered anywhere and are often appropriately compared with talcum powder. As seen in Fig. 2, 10 to 29 percent of the fines will pass through a 0.0017-in. screen opening, which is the smallest screen size used in a standard sieve analysis. Composite sand samples obtained from rubber sleeve cores were used in these sieve analyses. Since rubber sleeve cores can be recovered in a relatively undisturbed state, these samples are considered to be the best for distribution analysis.

The sand distributions obtained by sieve analysis were then used to determine the proper size screens and gravel to be used. Based on the sand distributions shown in Fig. 2, initial recommendations called for the use of three sand-control systems. These were an unpacked 0.008- to 0.015- to 0.025-in. triple-wrap screen, a 0.016-in. single-wrap screen packed with 0.017- to 0.033-in. gravel, and a 0.020-in. single-wrap screen packed with 0.040- to 0.060-in. gravel. packed with 0.040- to 0.060-in. gravel. Other methods tested included several additional single-wrap screen and gravel combinations as well as both unpacked and packed triple-wrap screens. The current techniques involve packing 0.020-in. single-wrap screens with 0.040- to 0.060-in. angular gravel in both open-hole and cased-hole completions.

Initial Triple-Wrap Screen Completions

Two types of sand control were initially used in Trinidad from late 1971 until mid-1972. One type was an unpacked 0.008- to 0.015- to 0.025-in. triple-wrap screen (see Fig. 3) developed by Amoco Production Research Co. and the other was a single-wrap screen with a gravel pack. The theory behind the triple-wrap screen was that the formation would "self-pack" around the screens as the well was produced. The multiple wraps of different gauge openings were expected to bridge the largest sand grains at the outer screen, intermediate size grains at the middle screen, and the smallest grains at the innermost screen. Thus, the 3 or 4 days of expensive rig time required for a conventional gravel pack would be eliminated.

JPT

P. 972