This paper presents a new concept, theoretical formulations, and field test results of the loss prevention material (LPM*) developed for use in many possible applications such as highangle and horizontal well drilling, drilling through severely depleted formations (to optimize casing requirements), drilling through highly tectonically active areas (i-e., regions of overthrust faults and salt dome structures) where the in situ rock stresses are high and directionally unequal. Both open-hole microfractures and 5000-ft open-hole leak off tests using LPM were successfully conducted in our wells in Newkirk, Oklahoma, and Ventura, California. LPM is a specially selected (material strength and specific gravity) and narrowly sized granular material which, after being fully mixed in oil or water based mud at an optimum concentration, can provide good protection to formations against lost circulation while drilling.Higher formation fracture resistance resulting from the use of LPM in drilling fluids can reduce or prevent the occurrence of lost circulation while drilling. This paper will show that a remarkable increase of 8.0 ppg in botehole breakdown pressure was achieved in one of our tests in the Newkirk well. An increase of fracture propagation pressure in the range of 3.0 to 6.0 ppg was recorded in the field tests. These results are in general agreement with our laboratory findings also discussed in this paper.References and illustrations at end of paper.

This paper presents analyses of five typical sand problems commonly observed in the field. The causes and progress of these sand production problems are explained using field data to help field engineers gain a better understanding of the various sand problems encountered. Strategies for minimizing these sand problems are also discussed.

More than 200% increase in fracture conductivity and permeability was obtained when a new degradable fluid-loss-control additive was used in place of silica flour (SF) in 40-lbm crosslinked hydroxypropyl-guar (HPG) fracturing-fluid systems. The new additive, an organic acid particulate (OAP), slowly degraded into water-soluble monomeric units at temperatures ~ 150°F after fracture stimulation experiments. The high-acid-content degradation product then acted as an excellent HPG gel breaker and effectively cleaned the proppant packs.As a fluid-loss-control additive, the measured wall-building coefficients were as good as, or better than, those of SF in crosslinkedgel, linear-gel, and N 2 -foam systems. This paper summarizes a 2-year study of the evaluation and application of this new product in fracturing-fluid systems. IntroductionRecent studies showed that HPG gels used in fracturing-fluid systems cause significant proppant-pack damage. 1-5 This study was aimed at finding a way to minimize fracture conductivity damage while HPG gel is used as a base fluid for fracturing stimulations.The new additive evaluated for a combined fluid-loss-control additive and gel breaker is an OAP-i.e., a polyester. The organic ester exposes increasing acid functional groups when degraded to soluble monomers. (The hydrolysis rates are a function of temperature and pH, as Table 1 shows.) Therefore, when the additive degrades after a fracture stimulation job, it imposes minimal formation damage. At the same time, when the degraded parts (acid) further break the linear and/or crosslinked gel used in fracturing fluids, the fracture conductivity is significantly increased. The HPG crosslinked polymer breakdown will occur because of the decrease in pH caused by the degraded parts of the OAP's and/or the crosslinking metal may be chelated by the organic acid monomer. Tyssee and Vetter 6 found that the HPG polymer degradation method may be backbone cleavage when the fluid-system pH is lowered.Because the OAP is a particulate, it will be retained in the gel filter cake when the fluid leaks off to the formation. As a result, the filter-cake cleanup should be much more efficient with a combined fluid-loss-control additive and gel breaker. The conventional water-soluble gel breakers leak off to the formation much more easily. To minimize the formation damage caused by unbroken gel during a spurt-loss stage, this volume could contain conventional soluble breakers. Our primary objective here, however, was to increase the fracture conductivity by minimizing the damage caused by the filter cake and residual gel in the fracture.Controlling fluid leakoff is also important in hydraulic fracturing. As Howard and Fast 7 show, fluid-loss characteristics of a fracturing fluid will influence fracture extension. To achieve an effective fracturing treatment, the fluids must have minimum leakoff while carrying the proppants. High fluid loss to the formation may cause ~remature termination of fracturing treatments by "sandouts." As a result, the OAP's have to b...

Summary The use of a new and different low-toxicity, low-pollutant oil-mud base fluid is presented. This low-polynuclear-aromatic (LPNA) oil differs from most other white mineral oils in that it is composed of 99+ % cyclic and branched paraffins with an average carbon number of C13. It contains less than 0.1 % aromatics and less than 1 % n-paraffins. This base oil composition provides for some interesting oil mud properties, which are discussed. Toxicity studies by an independent laboratory show the LPNA oil and the oil-mud cuttings to be substantially less toxic than diesel oil and the diesel-mud cuttings, respectively. Oil retention on the cuttings was shown to he less than for a comparable diesel mud. Laboratory formulation data, toxicity testing, and field test results are presented and discussed. These studies show the LPNA-oil-mud system to be an acceptable substitute for diesel mud systems and especially applicable to environmentally sensitive drilling locations. Introduction Advantages of Oil-Based Muds In recent years, there has been a marked increase in the use of oil-based drilling fluids. The widespread usage of these fluids has come about as a result of the proved advantages of oil-based muds over water-based muds in many difficult drilling situations. Oil-based drilling fluids have many favorable characteristics, including:excellent thermal stability for drilling deep hot holes;inherent protection against acid gases (e.g., CO2 and H2S) and corrosion caused by the presence of the continuous oil phase and the alkalinity control reagent (lime);capability of drilling water soluble formations (e.g., salt, complex salts, gypsum, and anhydrite) with little or no hole washout problems;improved lubricity, which aids in drilling deviated holes and reduces occurrences of "stuck pipe" problems;protection of producing formations from water intrusion, protection of producing formations from water intrusion, thereby eliminating clay swelling, which could result in reduced permeability of the pay zone; andability to drill thick, water-sensitive shale sections with relative ease, thus providing for gauge-hole drilling. This last characteristic is accomplished through the design of the internal brine phase of the oil-based mud. Such a system can be structured to provide an osmotic dehydration of the formation shale, thus preventing hole sloughing and providing for the stabilization of the borehole. providing for the stabilization of the borehole. When considering a drilling fluid program for a given well, the economics of a mud system is certainly of prime importance. In many cases, oil muds are not considered (although the drilling conditions warrant their use) because of their high initial mud cost (two to four times greater than most water-based muds). However, if the overall drilling costs are considered, the costs accompanying the use of an oil mud are usually comparable with or less than those of a water-based fluid. This is because most of the drilling problems are eliminated, resulting in substantial time savings. In addition, oil muds can be reused or resold following the drilling operation. Environmental Concerns The major concern in the use of oil-based drilling fluids revolves around their potential for adverse environmental impact, especially in potential for adverse environmental impact, especially in ecologically sensitive areas (e.g., active reefs or wetlands). In U.S. gulf coast drilling, current environmental regulations prohibit discharge to the sea of oil-based muds or any oil-mud cuttings that will cause a sheen. This is covered in Sec. 311 of the U.S. Federal Water Pollution Control Act (Clean Water Act) where Pollution Control Act (Clean Water Act) where Environmental Protection Agency (EPA) regulations disallow the discharge of any oil that will "cause a sheen or film or discoloration of surface water or adjoining shorelines - … "(In the context of this paper, the lack of a sheen, film, or surface discoloration on the water is referred to as "nonpolluting.") Sec. 402 of the Clean Water Act also regulates the discharge of pollutants by National Pollution Discharge Elimination System (NPDES) permits. Such permits allow for the discharge of drill cuttings, provided no oil is released that will cause a sheen or discoloration of the surface water. Whole oil mud discharges are prohibited in every case. Interim environmental regulations by the U.K. Dept. of Agriculture and Fisheries allow for the discharge of oil-based drill cuttings in North Sea waters, provided that the cuttings have less than 5 wt% oil (measured by retort) if diesel oil is used as the base fluid, or less than 15 wt% oil if a mineral oil is used as the oil-mud base fluid. Again, no whole mud discharge is permitted in any case. Oil Mud Components. JPT p. 137

In 1980 Conoco recognized the need for proper disposal of oil mud cuttings and has conducted both controlled "pilot-scale" soil farm studies and full scale field studies. Both the pilot scale and full scale studies show rapid reduction of hydrocarbons for both diesel oil and mineral oil base muds--up to 90 percent oil reduction within one year.