EPOXY-COATED SAND TAPS NEW GAS IN OLD WELLS

March 4, 1991
Lloyd Stutz Union Pacific Resources Victoria, Tex. Travis Cavender Otis Engineering Corp' Houston Joe Murphey Halliburton Services Duncan, Okla. Multiple-zone, dual-casingless completions combined with epoxy-coated sand to control sand production have increased gas reserves in Union Pacific Resources' McFaddin field of Victoria County, Tex. Sand production in this field has historically limited gas well life to the period during which dry gas is produced. Once water production begins,
Lloyd Stutz
Union Pacific Resources
Victoria, Tex.
Travis Cavender
Otis Engineering Corp'
Houston
Joe Murphey
Halliburton Services
Duncan, Okla.

Multiple-zone, dual-casingless completions combined with epoxy-coated sand to control sand production have increased gas reserves in Union Pacific Resources' McFaddin field of Victoria County, Tex.

Sand production in this field has historically limited gas well life to the period during which dry gas is produced. Once water production begins, the water conveys sand into the well bore, sanding out the well and damaging tubular goods.

Fig. 1 shows an elbow joint that eroded overnight once sand production started on a McFaddin field well.

Table 1 lists the incremental 417 MMcf of gas produced after the wells listed (Wells 1 7) were taken off production due to sand flow. These seven wells, on the average, paid out the cost of remedial treatment in 18 days of production after treatment. The remaining productive wells, as of Oct. 20, 1990, were producing 1.5 MMcfd.

Application of epoxy-coated sand before sand flow starts should be considered in fields known to produce sand in the late stages of hydrocarbon production.

In the McFaddin field, there has been no indication of formation permeability damage resulting from the use of epoxy-coated sand packs for sand control. Also, this type of sand control is not hindered by having to completely drill out the sand column in slim-hole situations.

FIELD CHARACTERISTICS

McFaddin field is geologically and structurally a very moderate anticlinal feature without great relief. The field is situated on the downthrown side of a northeast-southwest fault. Dip is down toward the coastline.

Producing zones in the field are Miocene, down to about 3,700 ft, and Frio below 3,700 ft. To help protect the formations, cementing strings are limited to 4,000 ft/stage.

Permeability is about 5 md. Sands with significant cumulative production are at 1,900, 2,150, 2,200, 2,800, 3,000, 3,400, 4,000, and 5,000 + ft.

The production is characterized by the change from dry gas to gas in water, and then to sand, gas, and water. The latter event historically has signalled the end of commercial value for the well.

WELL COMPLETIONS

Fig. 2a shows the typical completion method used on McFaddin field wells. In these wells, gas production ceased when water production started.

One attempt to stop sand flow is illustrated in Fig. 2b. In five wells, wire-wrapped, epoxy-coated screens were installed to filter out sand.'

Two of these completions were successful for a short time. In one well, the production increased by 10-15%. One other well had a negligible production increase, and three wells had no increase at all. A major weakness to this design was the small ID of the screen device. This acted as a choke in the well.

The amount of water that flowed with the gas dictated a requirement for an open hole filtering system to minimize sand production. Epoxy-coated sand packs became the next generation of sand control.

Fig. 3 illustrates the permeability of epoxy-coated packed sand. The treatment allows hydrocarbons and other formation fluids to flow through while holding formation sand in place.2-5

Many different uses for sand against sand have been found over the years. Rensvold established that resincoated gravel packs have very high permeability and are apparently unaffected by hot brine even after a flow of 30 million pore volumes.

Regression analysis was used to establish a curve for each system, relating pore volumes of brine to compressive strength (Fig. 4).

Resin-coated sand has been used for the repair of damaged slotted-liner gravel packs without the necessity for removing the liner from the well. A small workover rig with concentric or coiled tubing can be used to perform this treatment .6

Another sand-control process successfully applied is a formulation of permeable resin-fill material placed in a shot open hole to fill the large voids. Excess material is then drilled out and underreamed to allow a liner to be run and cemented in place. This method converts multiple-shot open hole completions into cased hole completions.'

EPOXY-COATED SAND

The key ingredient allowing construction of the sand filter in the well bore is internally catalyzed epoxy-coated pack sand conveyed to the well bore in water-based gel (80 lb/1,000 gal). Once the epoxy resin sets, the pack sand forms a permeable barrier allowing hydrocarbons and other formation fluids to flow through while holding the formation sand in the formation.

Typically, resieved 20/40 mesh Ottawa sand and an epoxy-resin formulation are thoroughly mixed in a solution of gelled brine. During mixing, the resin adheres to the surfaces of the sand, coating each particle.

A scanning electron microscope shows that although the mixture forms a block with great compressive strength, pore spaces remain open providing permeability in the 100 darcy range (Fig.3). 7 8

The resin-coated sand is pumped into the well at a concentration of about 15 ppg of gelled brine until sandout occurs in the perforations. Resin-coated sand then extends above the producing formation.

The gel breaks before the resin sets. Therefore, the pack sand settles into a better pack before the epoxy hardens. After an overnight cure, the consolidated sand pack is drilled out to reduce any pressure drop caused by producing through the sand column.'

The well produces with the formation sand locked by epoxy-coated sand left in the perforation tunnels. Figs. 2c and 2d illustrate the application of epoxy-coated sand to well bores producing sand with gas and water.

In this field, the injection pressure is limited to 800 psi to avoid formation damage. The application procedure is as follows:

  • Clean out sand down to and below the zone of interest using 1 1/2-in. tubing or coiled tubing. Pump KCI water or formation brine.

  • Leave the cleanout fluid above the zone of interest.

  • Pump a spearhead of 3% clay-control material containing the surfactant.

  • Pump a 3 bbl spearhead of hydroxyethyl cellulose (HEC) polymer mixed at 80 lb/l,000 gal to control fingering of the sand slurry into the fluid below.

  • Pump 4 bbl of internally catalyzed, epoxy-coated, resieved Ottawa 20/40 mesh sand.

  • Pump 3 bbl push pad of HEC polymer (same as Step 4 above).

  • Flush to screenout or within 100 ft of perforations with 3% clay control H2O or field salt water. Note that the injection pressure for all pumping steps is 800 psi. At the end of pumping, the pressure rises as the slurry hits the perforations. When the pressure reaches 1,300 psi, shut the well in under pressure. The pressure will dissipate on its own.

  • Let the well set overnight.

  • Drill out the sand slurry all the way to the bottom of the sand consolidation.

  • Slowly bring the well on production.

ACKNOWLEDGMENTS

The authors thank the management of Union Pacific Resources, Otis Engineering Corp., and Halliburton Services for permission to publish this article. They gratefully acknowledge all who helped in preparing this article.

REFERENCES

  1. Technical data sheets of several wire-wrapped screen manufacturers. e.g., Howard Smith Screen

    Co.: "Oil Well Screens," September 1982.

  2. Murphey, J., "Gelled Water Epoxy Sand Consolidation System," U.S. Patent 4.216,829, August 1980.

  3. Rensvold, R.F.. "Sand Consolidation Resins-Their Stability in Hot Brine," Paper No. 10653. SPE Formation Damage Symposium, Lafayette, La., Mar. 24-25, 1982.

  4. Halliburton Services, "Hydrocon-E Epoxy Sand Control Procedure," October 1983.

  5. Murphey, J., Roll, D. L., and Wong, L., "Resin-Coated Sand slurries for Repair of Damaged Liners," Paper No. 13649, SPE 1985 California Regional Meeting, Bakersfield, Calif., Mar. 27-29, 1985.

  6. Darr, C. D. K., Brown, E, K., and Murphey, J., "A Method to Convert Multiple-Shot Section Openhole Completions into CasedHole Completions with Zonal Isolation," Paper No. 15009, SPE Permian Basin Oil and Gas Recovery Conference, Midland, Tex.. Mar. 13-14, 1986.

  7. Nelson, C., Wilson. B., and Stadleman. J.. "Resin Coated Sand Slurry Pack Gas Deliverabilities: Field and Laboratory Results," Paper No. 11984, SPE 58th Annual Technical Conference and Exhibition, San Francisco, Oct. 58, 1983.

  8. Constien, Y. G., and Mayer, M. H. "What! No Screen? Gravel Packing with Water-Carried Resin Coated Gravel," 3rd Symposium of Formation Damage Control of the SPE, Lafayette, La., Feb. 15-16. 1978.

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