Sand Control Systems Research Articles

Monitoring sand dune advance in the Taklimakan Desert

The migration rate of sand dunes is important for the design of the sand-control system in the Taklimakan Desert. Sand dune movement was monitored in a sample plot along the desert-crossing highway by means of a topographical survey in late 1991, 1992 and 1993. The results reveal that most of the morphometric parameters of the dunes are not as well correlated as they are generally supposed to be. The mean advance rate of the dunes was 7.29 and 5.56 m year −1 in 1992 and 1993, respectively. The advance direction is towards the SW, approximately in accordance with the local resultant wind direction. The advance rate of the dunes was controlled by the local wind regime and dune morphometry. However, the relationships between advance rate and the morphometric parameters of the dunes are variable for the immature dunes. The small scale and immaturity of the dunes, insufficient sand supply, and complex wind modes are responsible for the complex dune parameter relationship, involving frequent changes of dune morphology, as well as changes of dune advance rate.

A History of Sand Control in the Teak Field

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

Controlling Sand With an Epoxy-Coated, High-Solids-Content Gravel Slurry

A new sand control process, effective in either old or new wells, has been applied successfully in more than 600 wells in Louisiana and Texas. Here are a review of field results and an outline of some important aspects of treatment design such as batch size, pump rate, gravel size, positioning of down-hole equipment, and the pumping sequence of fluids and slurry. Introduction The current emphasis on disaster prevention in offshore wells combined with the need to produce all wells at their maximum efficient rate has increased the need for effective sand control systems that do not cause impairment. A longstanding problem has been that of controlling sand in wells producing sizable quantities of it. In the past, two of the most widely used sand control methods have been gravel packing and in-situ sand consolidation. Although both methods have enjoyed considerable success, they have not always been as effective as desired. Neither method has proved effective more than half the time in treating old wells. The desire for a sand control method that would have the advantages of gravel packing without the susceptibility to shifting has led to the development of a number of processes that call for placing resincoated gravel across the producing interval. Essentially, the gravel is coated with resin at the surface and is carried into place in the well by a carrying fluid; then the resin either is allowed to cure or is flushed with a catalyst solution to effect cure. The Process In this process the gravel is placed as a concentrated slurry in a viscous carrying oil. Either of two internally catalyzed epoxy resin formulations is used to lightly coat the gravel. The slurry of resin-coated gravel is squeezed out be perforations until a screenout occurs or, in some cases, until a predetermined amount of slurry has been placed. In either case, the squeezing of the slurry is usually stopped while there is still enough slurry in the casing to leave a cap of the gravel in the casing above the perforations. In some cases where no screen-out is obtained, several barrels of excess slurry is squeezed and another batch of slurry is pumped into the well. After curing, the resin-coated gravel left inside the casing is drilled out, and the well is returned to production. At the writing of this paper, the new process has been applied in more than 600 treatments. The treated wells generally have been oil wells with perforated intervals ranging in length from 2 to 31 perforated intervals ranging in length from 2 to 31 ft. A few treatments have also been performed in gas wells and water injection wells. All but two of the treatments have been in cased and perforated intervals. One of the two noncased holes treated was a California well in which a slotted liner had failed. The liner was perforated in the area where sand was being produced, and two 10-bbl batches of slurry were pumped produced, and two 10-bbl batches of slurry were pumped to repair the screen. After the treatment, sand-free production was obtained. production was obtained. The treatment results in general have been very encouraging. Between 80 and 90 percent success has been obtained in treating both old and new wells. Naturally, changes in procedure have evolved since the method was first introduced to the field in late 1971. JPT P. 1215

Control of Unconsolidated Sands in Waste-Disposal Wells: ABSTRACT

Sand control methods were first used in water wells, and later, modified methods were applied to oil and gas wells. The most recent application for sand control is in waste-disposal wells. The increasing use of unconsolidated sands as disposal zones has created a need for better sand-control systems. We suggest that the primary causes of sand control problems in disposal wells are: (1) greater completion intervals, (2) intermittent operation of the well, and (3) chemical characteristics of the injected effluent. Therefore, successfully to prevent sand production in disposal wells, consideration must be given to: (1) formation characteristics, (2) completion fluid, (3) type of completion, and (4) completion method. Two universally used methods of sand exclusion, with suggested modifications when applied to disposal wells, are the method of in-place sand consolidation with plastics, and the use of gravel packs in conjunction with sand screens. Sand consolidation has limited application owing to the large completion intervals normally used in disposal wells, and to possible chemical reactions with injected effluent. However, a gravel-packed-sand-screen completion generally eliminates the three primary causes of sand production in disposal wells. Factors of prime importance are (1) the drilling and completion fluids, (2) formation grain size and composition, (3) size and amount of gravel, (4) pumping rate, (5) pressure, and (6) gravel concentration. Field and laboratory data show that the method of gravel-packed-sand-screen completions can be used successfully over intervals as large as 500 ft in unconsolidated Frio sands. End_of_Article - Last_Page 2084------------