A universal fluid (UF) is typically a water-base fluid that has been treated with finely ground blast furnace slag and that still maintains the appropriate characteristics of a good drilling fluid. The slag becomes concentrated in the filter cake formed while drilling permeable formations and slowly sets to form a hard layer intimately bonded to the formation. True zonal isolation can be obtained by using a UF and subsequently cementing with slag-based mud solidification technology. Complete mud displacement and efforts to remove filter cake are not necessary prior to cementing since the solidified UF filter cake bonds strongly both to the formation and to the cement and since undisplaced portions of the UF set up as well. The universal fluid (UF) has been developed primarily out of the need to improve cementing in horizontal and extended-reach wells. To date UFs have been used to improve zonal isolation and to reduce or prevent lost circulation or cement fallback during drilling and cementing. Two Diatomite wells in the Belridge Field, California and the vertical portion of one horizontal well in the Midway Sunset Field, California were successfully drilled with a UF and cemented with slag mix cement slurries. Also, a well in the Midway Sunset Field, where losses are routinely experienced, was drilled with a UF specifically to control lost circulation, and no losses were experienced. Five wells in the Peace River area in Canada were successfully drilled with aUF to prevent cement fallback upon cementing.
The objective of this laboratory study was to correlate the dynamic fluid loss (DFL) with the static [API high-temperature/high-pressure (HTHP)] fluid loss, the sticking coefficient, and the fluid-loss-control-agent (FLCA) concentration in oil muds. This was done as a continuing effort to use oil-mud FLCA's more efficiently in the field and to reduce pipe-sticking problems associated with deviated holes. Data were obtained with 13-lbm/gal [1558-kg/m3] inverted-emulsion muds by use of four different types of FLCA's over wide concentration ranges, but within the limits of reasonable field usage.The DFL data (at 250°F [121°C] and 500-psi [3447-kPa] differential pressure) were obtained with newly developed cells in which filtration occurs in an annulus around a central permeable core. An asymmetric buildup of mud solids and fluid channeling in the annulus suggest a mechanism that would greatly increase pipesticking tendencies in deviated wellbores.The DFL decreased with decreasing static fluid loss. The laboratory-measured sticking coefficient, which should correlate with differential-pressure sticking in the field, was reduced as fluid loss decreased. The fluid loss generally decreased with increasing FLCA concentrations, with the major reductions occurring at concentrations of about 4 Ibm/bbl [11.4 kg/m 3 ].
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Two new benefits derived from the use of a Universal Fluid (UF) have been demonstrated:reduction of the hole washout volume andsolidification of excess drilling fluid and drill cuttings for environmentally acceptable on-site waste disposal. A UF containing about 30 lb/bbl blast furnace slag was used as a drilling fluid while drilling a recent south Louisiana well in an effort to reduce hole washout and to demonstrate that the solidification of the UF and drill cuttings would provide an environmentally safe material which remains on-site and can be used for location maintenance, road construction, and land fill or other uses. The UF was used while drilling a 9 7/8-in. hole from 3,125 ft to the casing depth of 10,600 ft. The slag content ranged between 25 and 30 lb/bbl, while the UF weight was increased slowly from 9.4 lb/gal to 12.2 lb/gal. Caliper logs indicated that the average diameter of the UF-drilled section was 10.88 in., considerably better than the 12.85 in. of the same section of a previously drilled offset well. Of the total 147,000 lb of slag used, about 30% remained in the UF, about 22% was deposited as filtercake, and about 21% was discharged with the cuttings through solids control equipment. A concept of rig-site drilling waste management involving solidification of the UF wastes is elaborated and related lab and field data are presented. The necessary amount of slag for solidification is already in the UF and solid wastes, but additional slag can be added depending on the final product firmness desired. To demonstrate the waste solidification process, an additional 20 lb/bbl slag was mixed with a 40-barrel batch of the excess waste in a "V," -bottomed auger tank. The UF mixture was allowed to harden on location and successfully used for land fill. This paper shows that the UF can protect the drilled wellbore and can be economically treated and used for on-site disposal. P. 785
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Successful drilling of deep oil wells critically depends on drill fluids designed for specific down hole conditions. A new dynamic time-and-money saving circulation system stabilizes and tests high-temperature drilling fluids more accurately and reliably than previously possible. In this new system, a volume of mud is repeatedly pumped from an atmospheric pressure reservoir through a cycle of heating, high temperature shearing, cooling, low temperature shearing, and finally is returned to the reservoir. The system, which provides a laboratory mud equivalent to a mud produced in a deep high-temperature well over a prolonged time, is here described and contrasted with conventional test systems. Introduction Very few laboratories presently can formulate and test stable high-temperature drilling fluids in less than one to three weeks. This paper describes a compact new circulation system which significantly reduces preparation and evaluation time to a maximum of 48 hours and, for moderate temperature and shear fluids, a minimum of approximately 15 hours. The savings in time, money and manpower are obvious to engineers, drilling managers, and laboratory personnel accustomed to waiting out the tedious weeks required for conventional bomb methods. Moreover, comparisons with conventional methods indicate two further superior features of this new circulation system: mud and mud components stabilize more completely; and laboratory muds thus produced more accurately represent good field muds produced after extended high temperature drilling. For those of us whose livelihoods depend on our ability to provide superior research services, our essential task is to provide superior research services, our essential task is to provide quickly and efficiently the best possible drilling fluid provide quickly and efficiently the best possible drilling fluid materials for ever-deeper wells drilled in different parts of the world under widely differing conditions. Clearly, we must strive to anticipate actual drilling conditions, and to develop and test materials to withstand those conditions. The testing problems multiply by leaps and bounds as well temperatures problems multiply by leaps and bounds as well temperatures increase, and we all face the perennial problem: How to quickly obtain and test drilling mud in the laboratory which accurately simulates the muds produced during field drilling? Conventional laboratory stabilization methods generally involve high temperature aging of mud in small rotating pressure cells, or bombs, where frequent cooling, stirring, treating, cell resealing, and reheating provide continued aging. To yield sufficient amounts of good stable mud for high temperature tests, those procedures demand many cells and samples, and one or two weeks of daily treatment. Moreover, regular mud property analysis is feasible only when aging is interrupted. property analysis is feasible only when aging is interrupted. Since bomb methods require extensive manipulation, laboratory procedures are often simplified to save time. The problem with short cuts is that erroneous test data may result from continued changes in unstable clay systems which alter the actions of treating chemicals. To test muds more correctly without use of inadequate bomb methods, other circulation systems have been designed. These include those developed by Kelly and Hawk (a large, automated, closely controlled system in which previously stabilized muds can be tested precisely) and de Lautrec (known as the Mud Link, and used for detailed mud testing at well bore temperatures and pressures).
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