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Collaborating Authors
Drilling Fluids and Materials
ABSTRACT N Since the Amendments to the Resource Conservation and Recovery Act in 1980, the regulation of solid and hazardous wastes has taken quantum leaps forward. As a result of intense industry effort, the Amendments to XCRA provide for the exclusion of special wastes as hazardous wastes until and after proper study by EPA. Within the purview of "special wastes" are included produced brines and drilling fluids. The Act mandates EPA to study these wastes and report to Congress as to the necessity to continue their exclusion status. Based on contact with EPA's Office of Solid Waste, EPA has not yet completed its study of produced brine and drilling fluids. As a first step, EPA has contracted for: (1) a review of state regulations pertaining to these wastes and (2) a literature search relative to research available on these wastes. API continues to share with EPA research efforts relative to industry findings as to the fate and effects of produced waters and drilling fluids. As you know, these discharges are addressed at great length in the voluminous EPA comments and hearing records relative to the establishment of general permits in the offshore areas. Additionally, API has and continues to study the impact of drilling mud pits at onshore locations. Presently, API is planning a fresh water drilling mud pit study where the contents of a new site will be monitored from before the site is built, through the drilling phase and for some time after the pit is closed. A 1ocation.in the Gulf Coast Area will be selected and pre-drilling monitoring wells drilled. Data relative to seasonal ground water movement will be collected prior to construction of the pit. During the life of the pit, an accurate inventory of the discharges to the pit will be maintained. The pit will be constructed using a natural clay bottom. Following drilling, a decision to close will be made based on the inventory and monitor well data. Monitoring will continue for up to eighteen months following closure. This pilot site will provide information necessary to continue the pit study in other soil and climate areas of the United States. The information from this study will allow for a Best Management Plan for the pit constituents and ultimate closure of fresh water drilling fluid pits. Further, it should provide ample data relative to the fate and effects of various mud systems and additives on groundwater. You should be aware of the movement in the regulatory and legislative arenas to control these wastes. Either industry provides the basic research 1ead.ing to the best management of these wastes, or we will be regulated without full knowledge of their environmental impact. EPA has had sufficient emotional stimulation over the past five years to cause closer scrutiny of our operations relative to waste, disposal. Unfortunately, there is t an abundance of research in the area of fate and effects of impounded oilfield wastes. Consequently, the need for a more extensive study by API is obvious.
- Water & Waste Management > Solid Waste Management (1.00)
- Law > Environmental Law (1.00)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Well Drilling > Drilling Fluids and Materials (1.00)
- Health, Safety, Environment & Sustainability > HSSE & Social Responsibility Management > HSSE standards, regulations and codes (1.00)
- Health, Safety, Environment & Sustainability > Environment > Waste management (1.00)
I. INTRODUCTION Guar gels crosslinked with transition-metal ions are used as fracturing fluids in oil well completion. Gels are attractive because cross linking creates a fluid with sufficient viscosity to suspend solid propants while requiring only small amounts of par polymer. To simulate the fracturing operation and predict fracture geometry it is necessary to understand and model the rheology of guar gels. To date , the reproducibility of laboratory tests of guar gel rheology has been poor and models of gel rheology have involved only empirical modifications of the power-law fluid model. These empirical models are incapable of describing the effects of shear and time history on gel properties. The purpose of this paper is t o provide a working guide to the rheology, and characterization of guar gels . First , in Section II, we describe the experimental techniques used t o study guar rheology, which include dynamic oscillatory shear measurements and steady shear measurements. Dynamic oscillatory shear measurements are especially important in investigating gel structure because these measurements can be used to determine the number of network cross links. These measurements and their interpretation are discussed in detail, since they are probably less familiar to researchers in the oil production research area than are steady shear measurements. In Section III we describe the rheological Instruments used in this study. In Section IV the preparation of guar samples is detailed . The composition of the model guar gel used in this study was specified by the API steering committee. Our observations on the factors controlling gel rheology, including chemical effects , sample preparation effects , and flow history effects are presented in Section V. In Section VI a model that describes the rheology of gelling fluids is described. The model is based on the temporary network theories used to describe the rheology of polymer solutions. To this theory we have incorporated the chemical kinetics of metal ion adsorption onto the guar polymer backbone and subsequent polymer-polymer cross linking. In the final section recommendations for standard test procedures, for rheological instrumentation, and for future research are presented. I I. RHEOLOGICAL MEASUREMENTS A. Dynamic Oscillatory Measurements Dynamic oscillatory shear experiments which measure the linear viscoelastic response of materials are acknowledged to be the most valuable probes of gel o r network structure. Though steady shear measurements are necessary to duplicate process conditions , the oscillatory measurements give more insight into the properties of the gel than do steady shear measurements. When interpreted using classical network theory, linear viscoelastic measurements can be used to determine the kinetics of gel formation, the crosslink density of a gel , or the shear degradation of gel structure . The gelatin of polyvinyl alcohol and gelatin gels have been studied by a number of researchers ( 1 , 2 , 3 ) , and a t Princeton we have used these measurements to study polyacrylanide gels used as permeability control agents in enhanced oil recovery ( 4 , 5 ).
- Reservoir Description and Dynamics (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.88)
- Well Completion > Hydraulic Fracturing > Fracturing materials (fluids, proppant) (0.70)
ABSTRACT What is slip and why is it of practical importance? While the exact mechanism of slip can depend on both the type of dispersed system and the type of viscometer, one simple physical explanation of slip is illustrated in Figure 1. In this case, a cement slurry has exuded a film of water that adheres to the walls of the viscometer. Despite the fact that such a thin (1 x cm) film of fluid would be difficult to observe directly, this paper will show that it can dramatically reduce the apparent viscosity that one would measure. However, slip is magnified by the small hydraulic radius (-1 mm) of a typical viscometer. Consequently, apparent viscosities, based on laboratory data, may seriously underestimate the flow resistance in large diameter pipes and annuli if slip is ignored. What are the predicted effects of slip? The theoretical behavior of a material with a yield value, but without the complications of slip, is illustrated by the darkened squares in Figure 2. Note the characteristic flattening of the curve as the yield value (i.e., in Figure 2 the yield occurs at log 70 = 1.845) is approached. The predicted effect of a thin film (2.5 x cm) of water on the rheological properties of this same material is dramatic. In the first place, the apparent viscosity decreases with decreasing gap size (H = Rc-Rb, where Rb and Rc are the radii of the bob and cup, respectively). Furthermore, the curves with slip have distinctly different shapes near the yield value than the curve for which the slip velocity (Vs) was assumed to be zero. This result is important because it illustrates that even relative changes in rheological properties can be misleading if slip is ignored. One of the most significant predictions illustrated in Figures 2 is that slip provides a mechanism by which a material can flow at shear stresses below the yield value. We will soon see (Section IV) that cement slurries exhibit many of the characteristics of slip that are predicted in Fig. 2. How can we estimate the true shear rate when slip is important? The true shear rate (corrected for slip) is the quantity (V-Vs)/H. In order to calculate the slip velocity, we will assume that the apparent viscosity is a unique function of the shear stress. Consequently, if the stress is constant, then the apparent viscosity must also be constant. Likewise, if we assume that the slip velocity is a function of the shear stress without specifying the particular functional form of this shear dependency, then it follows directly from the definition of the apparent viscosity that the slip velocity can be calculated from the differences in the apparent shear rates(V/H) for two different size gaps.
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
ABSTRACT Deep drilling poses major problems when high temperatures, high pressures, and acid gases Are encountered below 17,000'. A combination of these items usually requires Extensive planning, exotic materials, long drilling times, and result in high costs. This paper discusses some of industry's accomplishments, current technology, and challenges associated with deep drilling And is conducted in water depths greater than 5,000'. INTRODUCTION America?s first oil well, drilled in 1859 by 'Colonel' Edwin L. Drake. Was a deep drilling Challenge to those involved. Although Drake reportedly said that they were prepared to drill to a thousand feet if necessary, oil was found at a depth of 69', approximately four months after the well was started in April, 1859. The Oil and Gas industry has continued to set depth record reaching the 10,000' mark in 193, the 15,000' mark in 1938 and the 20,000 mark was reached in 1972. Only two wells have been drilled below 30,000' in the United States. The first, a 30,050-footer in 1972, and the second , a 31 441-foot hole in 1974, were both drilled by lone star Production Company in Oklahoma's Anadarko Basin. The deepest well in the world is reported to be in the Soviet Union and recently drilled below 34,448'. The target depth of this well is 49212' (15,000 meters). This well, the USSR's SG-3 wildcat on the Kola Peninsula, west of Murmansk, was spudded in May, 1970, reached a depth of 31, 725' in July, 1979, and a depth of 32, 808' in May 1980. The Soviet's have reportedly said that improved technology probably will be required if the hole is to achieve target depth. The depth of well is not the main item to measure when determining the complexity of a deep well. Any time we stretch the capability of men, equipment, and technology, it is a challenge. For purposes of this review, a deep well will physically be referred to as being deeper than 17,000'. This depth has been selected to include a majority of the wells in the Tuscaloosa Trend of South Louisiana where many deep drilling challenges exist. If acid gases (H2S or CO) are produced at bottom hole temperatures above 300 ยฐ F, continuous corrosion inhibitor circulation may be required, and the well will be defined as a deep sour Gas Well( DSGW). Some companies have developed their own DSGW specifications for metallurgical control on deep, critical, acid gas wells since some requirement exceed API specifications.. Deep drilling in certain geological areas is not new. As can be seen in Figure 1, the 20,000' drilling depth was reached over 30 years ago and the 30,000 foot depth was reached over 8 years ago. The industry has had rigs capable of drilling to 30,000' for several years. However, if the well is to be an economical success, it must be safety completed to allow long term sustained production. Therefore, for evaluation, completion, stimulation, and initial production.
- North America > United States > Oklahoma (0.54)
- Europe > Russia > Northwestern Federal District > Murmansk Oblast > Murmansk (0.24)
- North America > United States > Texas > Anadarko Basin (0.99)
- North America > United States > Oklahoma > Anadarko Basin (0.99)
- North America > United States > Kansas > Anadarko Basin (0.99)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Health, Safety, Environment & Sustainability > Health > Noise, chemicals, and other workplace hazards (1.00)
ABSTRACT T Because drilling muds are frequently incorporated into soil near well sites and because little is known about the bioavailability of metals in drilling fluids, a greenhouse study was conducted to evaluate the effects of applying 3 water-base muds to 2 fertile soils on yield and metal content of Swiss chard (s ) and ryegrass (.). Two heat - treated, laboratory muds were prepared from barites low in toxic metals, whereas 1 drilling fluid contained a mixture of 4 low grade barites having significant levels of Hg, Zn, Pb, Cd, and was representative of a worst case situation .Muds were mixed with soil in 1:l and 1:4 ratios and unamended soil treatments were included as controls . Four or more cuttings of each species were produced over a 6-month period and yield and metal concentrations in tissue were determined for each cutting. Acetic acid-soluble, hot water-soluble, DTPA-extractable and total metals in soil were determined before and after cropping. Plants grown in mixtures containing 50% Battle Mountain drilling fluids or 20% and 50% mixed low grade barite mud had yields which were only 36 to 96% and 20 to 95%, respectively, of those from the control soils. The marked decrease in dry matter yields possible resulted from soluble salt or Na effects, Zn toxicity, and/or poor soil physical conditions. Application of moderate rates of "low metal" barite muds did not lower yield. The uptake of Cd, Zn, Cu, Pb, and As and the concentrations of these metals in plant leaves were related to the total amount of the metals in the rooting zone. The Cd concentrations in chard and ryegrass grown in soils treated with the drilling fluid made from four barites were 7 to 36 and 9 to 44 times higher than plants from unamended soils. Likewise, the Zn, Cu, Pb and As concentrations in chard were increased by 14 to 35, 1 to 3, 5 to 14, and 3 to 4 times by application of "mixed" barite drilling mud. The Zn, Cu, Pb, and As concentrations in ryegrass plants increased by 16 to 31, 2 t o 3, 4 to 25, and 3 t o 11 fold when soils were amended with the high metal mixed barite mud. These findings suggested that Cd, Zn, Cu, As , and Pb present in drilling fluids were, in part , available for plant uptake. Application to soils of drilling fluids prepared from "low metal" barite resulted in lower metals concentrations in plant leaves than was obtained with control soils. Mercury present in drilling fluid was not available for plant uptake. Barium, Ni, and Cr components in drilling muds were not readily taken up by chard and ryegrass. Extraction of drilling fluid or soil - drilling fluid mixtures with DTPA reagent or acetic acid was a satisfactory rapid test of availability of Zn, Cd, Pb, and Cu to plants . Hot water soluble As and Ni may be useful in predicting the availability of these two elements to plants.
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid management & disposal (1.00)
ABSTRACT The Tanner Bank study was conducted from January through March, 1977, on shell?s exploratory drill site, OCS P-0277 (Block 114), located 161 to determine the relative fate of mud and cuttings discharged under typical conditions; to qualitatively describe the nearby rock reef biotic community and determine the degree of disturbance resulting from semi-submersible anchoring activities. Current studies indicated discharge material would be adverted to the southeast (average current of 21 centimeters per second). Cutting materials settled rapidly; mud materials settled more slowly and formed a horizontals settled rapidly; mud materials settled more slowly and formed a horizontal plume. Plumes resulting from mud and mud/cuttings releases were measured for hydrographic changes (temperature, pH, salinity, dissolved oxygen and turbidity). Water samples were taken and analyzed for total suspended solids, chromium, barium and lead. Turbidity was the only water parameter showing significant change. Total suspended solids, chromium, barium and lead reached background levels within 200 meters. Dilutions of 400 to 1000:l were observed within three meters of the discharge pipe. Additional dilution of 100:l occurred within 100 meters of the discharge pipe. Due to steady currents and surge effects, no accumulation of cuttings materials was observed on the bottom. Comparison of sediment trap data and benthic grab samples showed that 75-90% of settle able material was transported from the immediate drill location. No accumulations of mud or cuttings were observed on the nearby reef. Observations were conducted from a two-man research submersible. Chain and anchor disruption of the bottom was minimal. Prior to OCS Lease Sale No. 35 in southern California, preliminary biological assessments of nominated tracts resulted in a series of tract specific lease stipulations. These were established in the "Federal Register", at 40 FR 51672 et seq., on November 6, 1975. Shell's lease on Tanner Bank (Block 114, OCS P-0277) was one of those designated as a "unique biological area." Lease Stipulation No. 6 reads in part: (A)operations in the zone five miles from the 80 meter isobath around these unique biological areas are restricted as follows: Drill cuttings and drill muds must be disposed of by barging the materials a minimum of ten miles from any 80 meter isobath surrounding areas of special biological significance. As a result of a cooperative effort between the Pacific OCS office of the Bureau of Land Management, Shell, and its contractor - Ecomar, a discharge monitoring program was designed to determine the fate of discharged mud and cuttings. In return for the implementation of this study, Stipulation 6 was waived for the one exploratory hole to be drilled. Bureau of Land Management and U.S. Geological Survey personnel were periodically present as observers throughout the project.
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
INTRODUCTION Analyzing for the oil content of produced water has become increasingly important over the last few years. More and stricter regulations are coming into force which limit the amount of oil that can be discharged with produced water. Analyzing for oil in water is difficult and frequently leads to ambiguous results. In fact, the selection of the method of analysis defines what is meant by "oil" . Because of these factors, there has recently been much activity in the area of analytical methods for oil determination in water. One such activity is being sponsored by the API Committee on Offshore Safety and Anti-pollution Research. The Ad Hoc Subcommittee on Oil Detection/Oil Removal (ODOR) under administration of the API Production Department Committee on Offshore Safety and Anti-pollution Research (OSAPR) was formed in the summer of 1974 under the Chairmanship of Mr. P. L. Gassett of Gulf Research and Development Company. The objective of the Ad Hoc ODOR Subcommittee is to define and implement appropriate research and development programs in areas of oil detection, measurement, and removal from produced water and solids. The research project which is being discussed in this paper is an outgrowth of an earlier review of research needs. Because there was already much activity in the development of analytical methods for oil in produced water, the Subcommittee decided to concentrate on certain problems in the analysis and interpretation of oil in produced water. Commonly used analytical methods involve extraction of the sample with an oleophilic solvent (e. g., carbon tetrachloride, freon, petroleum ether, n-alkanes, etc.) followed by a quantitative finish (e. g., gravimetry, colorimetry, infrared, ultraviolet). These procedures may give misleading results either by (1) misrepresenting the actual quantity of oil hydrocarbons) present in the discharge (for example, a study conducted jointly by the EPA and the Offshore Operators Committee Sheen Technical Subcommittee demonstrated that at high "oil" values, a gravimetric finish gave different values than an infrared finish) ; or (2) yielding numbers which cannot be used to properly interpret the performance of oil removal equipment. The latter problem results from the fact that oil removal equipment usually removes only the dispersed oil ; whereas the analyses results give measures of both dispersed and dissolved materials. Some of the variables that are thought t o cause the commonly used methods to disagree are: dissolved organic compounds, suspended solids, and production treating chemicals. For example, a method using a gravimetric finish is sometimes suspected of giving erroneously high results because suspended solids were extracted and measured as oil. Therefore, the ODOR Subcommittee has sponsored a research project (OSAPR Project No. 3) whose general aim was to show how various methods are affected by dissolved organics, treating chemicals, and solids. In October, 1975, as a result of competitive bids, a contract was awarded to the Institute for Research of Houston, Texas, to carry on the research. This paper summarizes the results reported by the Institute for Research (Reference 1).
- Water & Waste Management > Water Management (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.50)
- Government > Regional Government > North America Government > United States Government (0.50)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology (1.00)
- Health, Safety, Environment & Sustainability > Environment (1.00)
ABSTRACT Seven typical drilling fluids were mixed at ratios of 1:l and 1:4 liquid mud to soil with six soils; these mixtures were tested for their effects on plant growth. Beans and corn in pots in the greenhouse grew normally in a few mixtures, but in most instances it is concluded that too much soluble salts or too high an exchangeable sodium percentage was the cause of reduced plant growth. Additions of gypsum without leaching was ineffective. When leaching was accomplished using a high salt water in the first volumes of water passing through ( to keep the soil flocculated while exchangeable sodium was removed), plant growth was improved in most instances. The causes of high salt content were potassium chloride and sodium dichromate, mostly. The dispersing problem of heated soils caused by high exchangeable sodium percentages results from the high sodium hydroxide contents added to all muds. The high sodium problem, the formation of sodic soils, is solvable hut requires some wetting and drying cycles along with chemical amendments and leaching to accomplish. INTRODUCTION Drilling fluids (also to be referred to as -muds) are essential in drilling operations. The mud cleans the hole of drilling debris, cools the drilling head, seals off porous geologic strata, and performs other beneficial functions. Only limited areas are "contaminated" by small quantities of the muds left at the drill site when drilling is stopped. Nevertheless, the current concern to maintain a suitably clean environment requires that drilling mud waste be studied for any possible localized effects on soils or plant growth. Drilling fluid composition varies with the needs of the hole, especially its depth. Water is often used in shallow drilling depths, but additional materials, muds, are needed for deep holes. This research is concerned only with "muds"-- aqueous drilling fluids which contain large amounts of barite (barium sulfate ), small amounts of bentonite (a montmorillonite clay), and various other additives. LITERATURE REVIEW Almost no studies on the effects of drilling muds on soils or plant growth have been published. Most information on the effects on plants of the more than 600 brand-name additives used in muds has been deduced from studies other than those involving drilling muds. A preliminary study involving thirty-one individual mud components verified that plant growth was reduced by several materials. Diesel oil, high concentrations of potassium chloride, high additions of sodium hydroxide, some starch, somelignosulfonates, and high levels of sodium dichromate caused the most obvious effects. The phytotoxicity of diesel oil is well known by those involved in weed . control--it is often used alone as an herbicide. The short-chain volatile portions of crude oils, which include diesel oil, are the most toxic The effects of soluble salts, mostly from the potassium chloride and sodium . . dichromate, is to reduce plant growth more as their concentrations increase. The effects of soluble salts on plant growth are quite well documented and predictable. Most plants have severe growth reduction at soil-paste extract conductivities of about 8 to 10 mmhos/cm. Many mixtures of soil with what are considered to be heavy doses of soluble potassium chloride or sodium dichromate have produced conductivities of 12 to over 100 mmhos/cm; these are high values often completely inhibiting plant growth.
- Materials (1.00)
- Food & Agriculture > Agriculture (1.00)
- Energy > Oil & Gas > Upstream (1.00)
ABSTRACT The Oil Detection or Removal (ODOR) Subcommittee of the API Committee on Offshore safety and Anti-pollution Research (OSAPR) was formed in the summer of 1974 under the chairmanship of Mr. P.L. Gassett of Gulf Oil Company, U.S. The objective of the ODOR Subcommittee is to define and implement appropriate research and development programs in the areas of oil detection, measurement, and removal from produced water and solids. The need for work in this area was defined as a result of industry response to an OSAPR questionnaire dealing with needed safety and antipollution research. Figure 1 shows the response from that questionnaire relating to anti-pollution research. The first topics in Figure 1 (e.g., Oil on Sand- Removal and Disposal of Sand Oil on Cuttings-Removal and Disposal of Cuttings; 011 In Water-Measurement; Oil In Water-Methods for Removal) were the top vote getters in the survey. Efforts of the Subcommittee in its first nine months of existence have been concerned with attempts to define specific areas where research is needed, to identify other groups working in the same areas, and to formulate research proposals In areas where there is a clear need not being covered by other groups. Summaries of activities in each of three main topic areas are given below. OIL MEASUREMENT IN PRODUCTION DISCHARGES There is much current activity in the development of analytical methods for oil in aqueous discharges. The status of some of the methods currently available is indicated in Figure 2. In addition, the American Society of Testing Materials has two groups looking at additional analyses -- ASTM D-19.06 (range 0.5-30 ppm oil)and d ASTM D-19.10.09 (range 1 ppb to few ppm oil). With all of this activity, the Subcommittee does not feel it appropriate to fund further method development work. The Subcommittee does feel that there are certain problems in the analysis and interpretation of oil content in production discharges which may require further study. For example, how do solids in produced brine (sand, clay, iron oxide, etc. ) interfere with the reading of oil content using the various techniques? If there is a serious problem, method development research for the analysis of oil in the presence of solids may be appropriate. In addition, how do dissolved organic components (dissolved oil and treating chemicals ) affect the oil content reading? This latter question is important to the proper interpretation of the capabilities of oil removal equipment most of which is designed for removing dispersed oil. The ODOR Subcommittee is currently addressing questions such as these and should be ready to submit a proposal to the OSAPR Committee at their next meeting. OIL REMOVAL FROM WATEB The need for further research in the area of oil removal from produced water is not clear. The Sheen Technical Subcommittee of the Offshore Operators Committee has gathered data pertaining to current operational capabilities in the Gulf of Mexico. This data has been subsequently analyzed in an attempt to define
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > North America Government > United States Government (0.53)
ABSTRACT ABSTRACT New well completion technology has been developed to deal with problems unique to arctic areas. Some of these problems result from the interaction of permafrost with the wellbore. During drilling, completion, and production, some thawing of permafrost around the wellbore occurs. If wells are not produced immediately after completion, or if production is interrupted at a later time, the thawed region around the wellbore will begin to refreeze. Refreezing of the permafrost can lead to two types of problems. First, as water in the thawed region is converted to ice, its volume increases. This results in high fluid pressures which are imposed on the outer casing. Full scale field tests, extensive laboratory measurements of the mechanical and thermal behavior of permafrost, and theoretical and computer studies have led to an understanding of these pressures. External refreezing pressures calculated for normal operating conditions are in a range that can be tolerated if the proper casing is selected. A second potential problem is the refreezing of fluid within the wellbore system itself. If freezable fluids are left in annuli during the completion process, the possibility of high internal pressure exists due to the volume increase when freezing occurs. Because of the low pipe expansibility, pressures can rise to values which will cause collapse of inner strings or burst of outer strings. There are several practical approaches to avoiding this potential problem. This paper describes a unique displacement process which has been used to replace freezable fluids with nonfreezable, thermally insulating casing fluid. INTRODUCTION The discovery of oil in arctic areas has led to significant changes in drilling and well completion practices. The harsh winter environment has necessitated substantial changes in surface operations. In a less obvious wag, subfreezing temperatures have also created subsurface problems of considerable significance. The subsurface problems considered in this paper result from the interaction of permafrost with the wellbore. Permafrost of various thicknesses occurs in arctic regions where commercially significant hydrocarbon reserves may be found. Many wells have now been drilled-and completed on the Alaskan North Slope where approximately 2,000 feet of permafrost are encountered. Even thicker permafrost has been reported in Russian technical literature. During the drilling and well completion operation, some thawing of the permafrost is caused by the drilling mud which brings heat up from the earth below the permafrost horizon. Drilling can typically result in a thawed region of a few feet in radius. Production of hot oil for a long period of time can lead to thaw radii of several tens of feet, Ps29S the exact value depending on the operating conditions and the degree of wellbore insulation provided in the permafrost region. If the wells are not produced immediately after completion, or if production is interrupted at a later time, the thawed region around the wellbore will begin to refreeze. Refreezing of the permafrost can lead to two types of problems. First, as water in the thawed region is converted to ice, its volume increases.
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (1.00)
- Well Completion (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring (1.00)
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