This paper describes methcds and technology for contdfittg the cotmsivity of heavyweight brines. The conclusions are based on more than 5,(MOcorrosion data points genetated in the laboratory and actual field use of tie tecbnolog. Brines used in this study were single-, two-, and ,jhree-salt mixtures with densities varying from 8.4 to 19.2 ibm/gal [1007 to 2301 Wm31. 'f=.t mJWratures and pressures varied from 10Q to 500"F [38 to 260"CI and 1,CQOto 10,CHY3 psi [6.9 to 69 MPa], respdively, The tests v+?d in length from 1 to 90 days, and the tubing materials tested were 1028, 355, N80, and PI 10 steel.

iBSTRACT in a well. These factors include wel1 temperature, production gases, produced fluids, completion fluids The use of brines in oil and gas wells as a and corrosion inhibitors. 1~2 The chemical and physi-:ompletionfluid, workover fluid and packer fluid is a cal changes which some elastomers undergo in certain mnsnon practice. Salts consnonlyused to make these conditionscan be detrimentalto the productionopera-}rinesare KClj NaCl, CaClz, CaBrz and ZnBrz. tion (cost). Therefore, the selection of the proper compound from which to make the packer elements should Under certain conditions these brines are corro-be of utmost importance. sive, and corrosion inhibitors are usually added to reduce their corrosivity on the tubing, casing and To make the proper packer element selection, the iownhole tools used in the well. Brines also come environmentthe packer element will encounterthroughinto contact with the elastomers (packer elements) out its life in the well should be considered. Other sed on the downhole tools. Failure of the packer factors were also taken into consideration for this element either by hardening or softening can signifi-study. Several factors already covered by previous :antly reduce the time interval between workover authors, such as production gases and production operations. fluids, will not be covered in this puper.3-6 This paper primarily deals,with the effect of temperature, This study encompassed the testing of various completion fluid (brine) and corrosion inhibitors on types of commonly used packer elements at 250"F 70-durometer nitrile, 90-durometer nitrile and 80-(121°C) and 350°F (177°C). These elastomers were durometer chlorinatedpolyethylene(CPE) compounds. tested for 7 and 70 days. The physical properties of packer elements observed throughout the test periodsThe oil-field industry has gone almost completely were hardness,tensile strength and elongation.to the use of brines as the completion,workover and :::::~luids, because of their nondamagingcharacter-Brines selected for use in these tests were 14.5The salts primarily used to make these lb/gal (1.74 g/cc) and 16.5 lb/gal (1.98 g/cc) which brines-are KC1, NaCl, CaCl*, CaBrz and ZnBrz. The;: used CaClz, CaBrz and ZnBrz as weighting agents. salts can be of single, two or three mixtures. Corrosion i,ihibitors tested were (1) a film-forming is due to their low solids content. When muds are amine and (2) a low-molecular-weightorganic product left as a packer fluid, the solids tend to settle out which contained sulfur. while in the static state. These solids on top of the downhole tool will cause retrieval of the tool to be The types of rubber elements used in this study difficult and expensive.e were 80-durometerchlorinated polyethylene (CPE), 70durometer nitrile and 90-durometernitrile elastomers.Several authors have shown that sin le salt" brines have relatively low corrosion ratesg '?3 at low

The success of a gravel-pack completion depends on placement of gravel in the perforation tunnel area and the screen-casing annulus. Wellbore deviation is one of the predominant factors affecting gravel placement. As wellbore deviation increases, the gravitational forces and carrier fluid limitations may result in gravel settling (duning) and an incomplete packing of much of the perforation tunnel area, as well as a premature screenout of the screen-casing annulus.A completion technique is introduced that eliminates prob 1 ems associ a ted with gravel settling. The technique uses buoyancy forces to counter the gravitational forces on the gravel particulate. Particulate settling is minimized by decreasing the ratio of the particulate density (Dp) to the base fluid density {De).Verification of the concept includes test results from a gravel-pack model. The model is 18ft long with an inside diameter {ID) of 6.2 in., a screen and blank pipe size of 2-7/8 in., and a working pressure of 1,000 psi. The blank pipe length is 6ft and the screen length is 12 ft. There are 20 perforations that include a chamber to simulate a void space behind the casing.Test results include gravel-pack efficiency for variations in base fluid properties, wellbore deviation up to 90° {horizontal) and particulate density/ base fluid density ratios (Dp/Dc) from 2.65:1 to 0.8: 1. Recommendations for a treatment technique and low-density particulate specifications also are included.References and illustrations at end of paper. 227

This paper deals directly with heavyweight brines and the corrosivity of the brines. Methods and technology are described which can be used to control the corrosivity. The conclusions related to in this paper are based on over 5,000 corrosion data points generated in the 1aboratory and actual fi el d usage of the technology. Brines used in this study were single-, two-and three-salt mi xtures whose dens it i es vari ed from 8.4 to 19.2 1b/gal. The test temperatures and pressures varied from 100°to 500°F and 1,000 to 10,000 psi, respectively. Length of the tests varied from 1 to 90 days and the tubing materials tested were 1008, J55, N80 and PlIO.

Packing the annulus and perforations with gravel in highly deviated wells, especially horizontal wells, is difficult. As well deviation increases, pump rates and carrier fluid viscosities increase to prevent particle settling. Increasing the viscosity can reduce fluid leakoff and particle settling. Increasing the viscosity can reduce fluid leakoff and perforation pack efficiency. Gravel-pack studies have shown that placement perforation pack efficiency. Gravel-pack studies have shown that placement efficiency improves as particle density (Dp) and carrier fluid density (Dc) become closer. in an ideal system, these densities would be equal (Dp:Dc = 1). With this ideal design, no viscosity would be required to suspend the particles, thereby improving fluid leakoff and perforation packing. The use of sand as the packing material has limited the use of packing. The use of sand as the packing material has limited the use of such a technique because of hydrostatic overbalance. The introduction of a pack material whose density (1.65 g/cc) is 40% less than that of pack material whose density (1.65 g/cc) is 40% less than that of sand makes this technique available without the overbalance concerns. The paper provides the industry with technology which is applicable when gravel packing highly deviated (horizontal) wells. This paper describes:a new method of completing highly deviated and horizontal wells using low density particles and low Dp:Dc ratios,computer simulations performed to aid in designing completion techniques,printouts of the screenout pressure and pump rates,schematics of the well design,logs of the pack andwell performance. performance Introduction Gravel packing a highly deviated well using conventional products and completion techniques can be extremely difficult. In highly deviated wells, prepack screens are used, as an insurance step, in case the perforated interval is not completely covered. The prepack screen adds perforated interval is not completely covered. The prepack screen adds additional cost and may restrict production due to plugging by fine particles. ideally, nothing would change between a conventional pack and a particles. ideally, nothing would change between a conventional pack and a highly deviated pack. However, because of gravitational forces, alterations in the completion are required to successfully complete the well. This paper describes the successful gravel-packing operation on a 72 degree deviated well using a low-density particle (LDP) and standard gravel-pack screen in the Gulf of Mexico. The well is located approximately 135 miles (217 km) offshore from Cameron, Louisiana, in 175 ft (53 m) of water. The objective pays of the well are at 2,200 to 2,900 ft (671 to 884 m) subsea and located under a shipping fairway. To drill these upper and lower sands, the well had to be kicked off at the mudline and drilled at an average angle of 72 degrees with the surface location 300 ft (91 m) from the fairway and the bottomhole location 6,533 ft (1991 m) into the fairway (Fig. 1). The casing profile initially called for a 7-5/8-in. (194-mm) Uner, but because of excessive wear in the 10-3/4-in. (273-mm) casing, the liner was tied back to surface. The open-hole logs were obtained with a logging while drilling tool on the end of the drillpipe. All cased hole logs were run on coiled tubing electric line. This is 1-1/2-in (36-mm) coiled tubing with a multiconductor electric line through it. Gravel packing the annulus and perforations in highly deviated wells and especially horizontal wells is difficult. Gruesbeck et al. determined packing efficiency increases with- lower gravel concentrations, decreasing particle diameter, decreasing particle density, increasing fluid density, increasing pump rate, and increasing resistance to fluid flow in the washpipe/screen annulus. Shyrock found that in addition to the above parameters, reducing the length of blank sections In the screen and reducing the fluid viscosity increase packing efficiency. P. 387