Abstract ARCO Oil and Gas Company has drilled two horizontal drainhole wells in the Empire Abo Unit. A horizontal drainhole well is one in which the wellbore is turned from vertical to horizontal in a short radius and the horizontal hole is then drilled out some distance into the formation. These wells were drilled to evaluate the mechanical feasibility of the drilling process and to examine the effect producing through the drainholes would have on the well's tendencies to form gas cones. Although several problems were encountered while drilling the problems were encountered while drilling the drainholes, the drilling technique used does seem to be mechanically sound. The wells have not been on production long enough to fully evaluate their gas coning performance as compared to conventionally performance as compared to conventionally completed wells. This paper will briefly examine the gas coning problem in the Empire Abo Unit, discuss some of the techniques used to limit gas coning in the Unit, and review ARCO's experience with horizontal drainholes. Introduction ARCO Oil and Gas Company operates the Empire Abo Unit, located in the Empire Abo Pool of Eddy County, New Mexico (Figure 1). The Unit consists of approximately 11,000 acres and represents about 97% of the entire pool. Production is from the Permian (Lower Leonard) Abo Reef dolomite at a depth of approximately 6200'. The productive reef development is productive reef development is approximately 12.5 miles long and 1.5 miles wide (Figure 2). The cross-sectional view in Figure 3 illustrates the massive reef development. The main producing mechanism is gravity drainage which is now supplemented by the injection of the residue gas into the gas cap. The pool was discovered in 1957. Competitive development of the field on 40-acre spacing was rapid. The pool was operated on a competitive basis until 1973 at which time the Empire Abo Unit was formed. S.H. Christianson's paper gives a detailed description of the reservoir and discusses factors involved in the formation of the Unit. Prior to unitization, approximately 96 MMBO were produced from the Abo Reef. An additional 91 MMBO have been produced from the date of unitization through April, 1980. The Unit's current production rate is about 25,000 BOPD. production rate is about 25,000 BOPD. GAS CONING IN THE UNIT At the time of discovery, the Abo reservoir pressure was above the crude's bubble point. Competitive production of the pool resulted in a drop in pressure to below the bubble point and the formation of a secondary gas cap. By the early 1970's several wells in the up-dip area of the pool began to produce at gas/oil ratios (GOR's) in excess of the solution GOR indicating the production of free gas from the gas cap. Drill stem test information indicated that these high GOR wells were perforated below the level of the regional perforated below the level of the regional gas/oil contact. Localized depressions in the gas/oil contact around the wellbores (gas cones) were causing the high GOR production. production. Producing Empire Abo wells at high GOR's is undesirable for two reasons.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. 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 The Survey Steering Tool System available to the drilling industry today is a culmination of five years of successful field-proven development and progress. These five years, with thousands of hours of proven performance, point up the fact that a Survey Steering System will save many hours of valuable rig time. The saving of rig time may be accomplished in many ways. It matters not what the actual cost per day of the rig, the Survey Steering per day of the rig, the Survey Steering System will save enough rig time to economically justify the cost of using the system with a mud motor when a course change is necessary. Introduction Perhaps the most important consideration in using this system to save rig time is in keeping the mud motor properly oriented and drilling along the desired course. There are many other benefits to the operator that may not be readily apparent. The problems of Dog-Leg Severity are greatly minimized by using the system with a mud motor. Several years experience has shown the use of the Survey Steering System with a mud motor allows operators to drill some holes which previously were not economically feasible. Another rig-time saver is the ability to survey the hole while it is being drilled. The time required to orient a mud motor on a given well may take several hours for orienting alone, and then, if the mud motor should stall out just once, this time consuming procedure must be repeated. The ability to survey while drilling will allow the directional driller to maintain a desired course in order to arrive at the prescribed target in a minimum of drilling prescribed target in a minimum of drilling time. The general practice used by a directional engineering company is to design a program for the directional hole program for the directional hole establishing the course deviations along with the desired rate of angle change in order to achieve the required horizontal displacement to reach the desired target. Experience has shown that many hours of rig time are used in making correction runs with different bottom-hole assemblies in order to stay on the predetermined course.

Abstract Directional drilling is used extensively in the oil industry, and also has many uses in other fields. Early directional drilling is discussed in detail to familiarize the reader with its terminology and to help him more fully understand the need for improvements. In the past 10 years, directional drilling companies have developed many new, tools and techniques. Advantages and disadvantages of these improvements are pointed out in this article. Introduction Directional drilling, which was started in the early 1930's, has found a respected place in the oilfields of the world. In recent years it has become a highly scientific and technical profession. In the mid 1950's, engineers took directional drilling in hand and the established methods that were based entirely on experience began to give way to modern techniques. These techniques were designed to improve the mechanics of directional drilling and to reduce high costs of directional drilling jobs. This article presents the many improvements that have been made in directional drilling equipment and techniques in the past 10 years. The article represents the views of the author as obtained from experience as a directional driller, and from interviews with directional drilling representatives both in management and on the field engineer level. Uses of Directional Drilling The proper approach for illustrating these many improvements must begin with an understanding of directional drilling and its many uses. As applied to the oil industry, the deflecting of wellbores comes under three general headings. Sidetracking, in its most popular form, involves going around a fish left in the wellbore. Another example: when a producing reservoir is missed, a plugback and the accompanying oriented sidetrack can give a much more favorable bottom-hole location structurally. Sidetracking has been used often in secondary recovery work in both cased and uncased holes to move the bottom-hole location to an area of less depletion. A second general heading involves straightening or straightening up of a wellbore. This operation is mainly concerned with moving the bottom-hole location back to the proximity of the surface location. Typical applications would be drilling contract commitments, lease line obligations and bottom-hole well spacing requirements. A third general heading, and by far the most important, is planned directional drilling which has numerous applications, the largest being in offshore drilling operations. Platform-type directional drilling programs involving multiple wellbores have many cost-saving features, in both drilling and production phases. In multiple-well platforms of four to six wells, the initial costs would be equivalent to those of five or six individual vertical wells. However. with platforms of 12, 18 and 24 wells, economic operation is realized. Expensive rig moves are eliminated. The close proximity of multiple wellheads greatly simplifies gathering systems and production techniques. Under this same general heading fall relief wells that are drilled to kill uncontrolled blowouts. This application has no parallel in many instances. Another application involves inaccessible well sites. Typical examples are wells drilled under lakes and rivers, under populated metropolitan areas and difficult terrain such as mountainsides. Another use of directional drilling principles is the drilling of drain holes where many "roots" extend from a single wellbore in thick producing zones. These drain holes produce some of the most rapid drift angle buildups that are known, often 2 degrees/ft or angles completely horizontal. Other applications of directional drilling that are of interest would be drilling wellbores into shallow sulfur deposits and using super-heated steam to melt the sulfur for production. Completely opposite production techniques are planned for a potash field in Canada. Twenty to 25 wells are being directionally drilled to circulate a freezing medium and solidify underground water formations for a mining operation. Directional drilling has been used in recent years to tap underground nuclear explosion sites to obtain samples for radioactive analysis. Directional wellbores have been guided from mountain sites to intersect with tunneling operations for air purification purposes. JPT P. 469ˆ

ABSTRACT A new method of deflecting a well bore has been developed which eliminates , In certain situations ,the use of such tools as the whipstock, knuckle joint, or - spud bit, and which results in considerable savings The "jet-deflection method" was devised to eliminate the time-consuming practices of using the more conventional tools A conventional jet bit is used with all but one jet restricted, and this one jet of as large a diameter as the hydraulic system will permit By eroding the well bore on the side and bottom In which the large orifice is oriented , the bit tends to deflect the hole in that direction After the proper course is established, the same bit is used to drill ahead. The "jet-deflection method" has reduced the time Required to drill surface holes by two thirds, and wells are being directionally drilled in only a few days more than a straight hole When the deflection is small, the hole may be deviated and straightened up in the surface hole at slight additional cost over straight hole Only conventional bits have been used, with variations in the jets. However, it is believed that the range of usefulness of this method can be extended by the development of special bits and tools more adaptable to jet deflection INTRODUCTION In recent years, controlled directional drilling has become an important factor in the economical exploration of reserves which lie under inaccessible or very costly surface locations . With the advent of offshore development of the tidelands and the increase in town-side and river-bottom drilling, a boom in directional drilling as occurred Until recently the conventional means of deflecting a bore hole consisted of using three types of equipment the whipstock, the spud bit, and the knuckle joint All of these methods require considerable lost time as a result of tripping, changing bottom-hole assemblies, and circulating condition the hole. Additional equipment in the form of bits, hole-openers or pilot reamers, substitutes, small drill pipe, and monel pup joints are required. Several possible hazards are involved when using the older tools, the most serious of which is sticking the whipstock When this occurs and the tools cannot be jarred loose, a costly fishing job usually results A second danger when using a whipstock is the premature shearing of the shear pin, which is a frequent occurrence when running a whipstock In the hole. A third risk involved is the possibility of being unable to get into the rat hole after setting and drilling off of a whipstock. The last undesirable factor involves the course of a hole drilled with tools which have a predetermined deviation built into them The hole must be drilled until the course is a tool-set off and then a tool run. This often results in severe dog-legs which can later interfere with drilling and completion As the conventional tools in use were both time-consuming and risky , an improved method of gaining the objective was needed

Introduction few years, modern techniques and methods have The directional drilling of oil well bores as used in increased vastly the applications and possibilities of oil field practices is defined as the positive control of the science of directional drilling; it is with some of the direction taken by the bit while drilling is in progress. The techniques and methods now in use were f Such topics as "Directional Drilling Tools", "De Directional drilling Programs", and "Achievements of Direc - procedures are now a vitally important factor in tional Drilling" are discussed in detail in this report, augmenting the supply of petroleum products, and, with the emphasis on the more recent developments in addition, directional drilling is in many instances in techniques and tools. Directional drilling operations directional drilling problems over the past twenty have now been successfully completed under all the years, anticipates that the future trend for such varied conditions existing in oil fields throughout the operations will be toward simplification, and that world, and thus the practicability of directional programs some day directional wells will be drilled in as routine has been proven and has gained widespread a manner as straight holes are today. At the time this mettant plus de poids sur les progrès récents des paper was written, more than fifty directional jobs techniques et de l'outillage. Development of offshore oil have been killed in Oklahoma, Canada, Rumania, and structures has had wide application in the Wilmington, very recently a wild well was brought under control Elwood, Seal Beach, and Huntington Beach in Iraq by directional methods. Although there are other a productive portion of a lease; 6) deflecting an old full gauge tools on the drawing boards, the above depleted well to a new location in producing territory; mentioned tools have been given enough field trials 7) deflecting across faults or out of fault zones into to prove their worth under actual drilling conditions. The full gauge whipstock run, instead of being followed with a pilot reamer, is usually followed by a directional drilling setup, consisting of a bit, a reamer, and a short drill collar. Figure 1. with this type of setup, it is possible to use small single shot surveying equipment, and immediately The full gauge knuckle joint was developed before take a survey reading after the full gauge bit reaches the war and has since had fairly extensive field trials. This procedure saves the time necessary to This tool is extremely safe to run, very rapid in its withdraw the drill pipe in order to check the direction operation, and gives quite accurate results.

ABSTRACT This paper reports on the history, application, techniques, and basis of future development of directional oil-well drilling and surveying. A glossary of some of the terms used by the directional drilling engineer is included. Important considerations the planning and execution?s of a directional program are detailed, and the advantages and disadvantages of drilling deflected holes are discussed. It IS pointed out that, despite rapid past development of new tools and operating techniques, the need for additional development exists, notably in the improvement of devices for directional surveying. INTRODUCTION Within a relatively few years the status of directional drilling has changed from that of an common expedient to that of a routine drilling procedure, as a result of significant advances in the art of controlling direction holes. These advances have made possible the economic development of several oil fields in the United States, as well as the extension of many other fields into otherwise inaccessible areas. Conversely, the problems encountered in the drilling of these fields encouraged the development of new tools and operating techniques. Greatest progress, however, has been in the planning of the directional program. As a result, the effectiveness of the entire process is such that the planning, drilling, and production of deflected wells can be done in an orderly and economic manner. Responsibility for the planning and execution of a directional-drilling program is usually divided among several organizations or departments of one organization. This, In turn, implies that each person involved has a thorough knowledge of the entire procedure. This is particularly true of the petroleum engineer who is responsible for planning and supervising the directional program. He must be able to evaluate the suitability the of drillings sites, recognize the advantages and disadvantages inherent in different drilling procedures, and plan the wells in such a manner that geologic conditions are met, and that legal, contractual, and economic limits are not exceeded. Historical Background Some of the basic tools and procedures used in directional drilling have been known, at least in crude form, for decades. For instance, a man whose active experience in the industry dates from 1896 has informed the author that a t least 2 removable whipstocks were run on cable tools between 1897 and 1900. In addition, directional surveys were made by watching the course followed by an oil lantern which had been lowered down the bore hole on a line. Occasions arise today which cause engineers and directional supervisors to which that this uncomplicated procedure were applicable to their problems. Drilling booms in such areas as Signal Hill, Santa Fe Springs, Dominguez, and Huntington Beach were responsible for the rapid development of directional. drilling. The oldest and simplest method of directionally deflecting the well was that of orienting 'the entire rig, then blocking up one side of the rotary table so as to incline the kelly. The desired results were usually accomplished, although the method had several disadvantages, as both drill pipe and casing slips were difficult to set properly, and driving-chain breakage was Increased. However, the method is still used when it is desired to deflect the hole a t a very shallow depth.

ABSTRACT In this paper the author, after years of practical experience in the drilling of directional wells, discusses the various combinations of drill pipe, drill collars, reamers, bits, weight on bottom, pump pressure and table speed, which can be utilized to reduce the number of primary deflecting tools usually required. The influence of the stratigraphy and structure of the sediments to be penetrated are set forth, together with the methods used to overcome or control these influences. Precautions in the original plans for directional drilling and in the use and operation of equipment are also given. The paper concludes with a summary of the accomplishments in directional drilling and a discussion of the economic phase in its relation to vertical drilling. INTRODUCTION Directional drilling of rotary holes has become common Practice in the oil fields, with the recognition by the industry of the savings to be made by exploiting additional reserves in locations too costly or inaccessible for vertical drilling. Although this type of drilling was in limited use In the Signal Hill Field from about 1927 to 1930, the real development of high-angle directional drilling occurred during 1933, with the tapping of the rich oil pool lying beneath the tidelands off Huntington Beach, Orange County, California. Since that time many excellent papers and articles have been written about directed or whipstocked wells, but these have been for the most part confined to descriptions of the primary deflecting tools, the whipstock, knuckle joint and spudding bit, together with methods of running, orienting, and using them in a well bore. This paper is in no way meant to be a repetition of those former articles, but rather to give the practical side of directional drilling with control methods other than with deflecting tools. To run primary tools such as a whipstock, it is necessary to condition the hole, drill by the whipstock, drill ahead with rathole bit, and finally, expand the hole to full size of results are as desired. This may involve three or four extra roundtrips. Under some conditions two of these trips can be eliminated by using a differential bit in place of a hole opener. This type of bit, if crowded (i.e., forced by the application of sufficient weight), will follow closely the rathole-thus expanding the hole to full gage and permitting continued drilling without changing the bit. Considerable time lost by earlier methods is now saved by the use of the full-gage whipstock, full-gage knuckle joint, and the self-orienting drift master. Bottom orientation by various methods has greatly reduced the time of running primary tools, whereas the non-magnetic drill collar has likewise reduced time of taking directional single shots. Obviously, the advantage of directional drilling is the ability to direct the well bore along a predetermined course to a desired objective using the minimum number of primary tools. A great deal of knowledge and experience has been gained during the past 15 year concerning the results of using various combinations of drill-pipe and drill-collar sizes, use of reamers, types of bits, combinations of weight on bit, pump pressure, and rotary-table speed.

ABSTRACT This paper discusses some of the outstanding developments made in the drilling and completion technique during the last decade. Following a brief outline of the history of the development of various well-surveying instruments during the past 60 years, the most necessary requirements for instruments and surveying methods are stated. The various types of instruments, their operation, the correction of magnetic-compass records, the preparation of survey maps, and the frequency of taking records are described. The development of directed controlled drilling, its objectives and requirements, are explained. A brief description of the various tools used in this art of drilling and their method of use is given. Two principal methods of obtaining side-wall core samples in connection with electrical logging are described. A new method of determining the direction and the angle of the dip of the formation by orienting core samples off the core trays is depicted. INTRODUCTION In recent years there have been placed at the disposal of the oil-production industry a large number of instruments and tools, the use of which made the operators abandon the rule-of-thumb practices of long standing and substitute for them improvements in drilling and completion technique, with a far greater recovery of the oil underground than formerly was considered possible. Some of the outstanding developments during the last decade would include the following: Well-surveying instruments. Controlled directed drilling. Side-wall sampling. Determination of the direction of dip of core samples by using the residual magnetism of minerals in the core sample. A brief resume of these developments, the factors which should be considered when they are employed, and their coordination with the improvements of the drilling technique are presented herewith. Underground Well Surveying The art of well surveying is not so recent as might be supposed. More than 60 years ago mining engineers recognized the problems encountered when a well or test hole is crooked. The first known instrument for detecting the deflection of a bore hole was introduced in 1873 by G. Nolten, Dortmund. This comprised a glass bottle in which was placed an acid of sufficient strength to etch the interior of the glass when allowed to remain stationary for a predetermined length of time. Inasmuch as the axis of the bottle was parallel to the axis of the hole and the surface of the acid was horizontal, the angle of inclination from the vertical could be calculated. In conjunction with this instrument a compass was used, the needle of which could be arrested after a predetermined lapse of time. This instrument permitted only single readings. In 1884 E. F. MacGeorge brought out and tested at Sandhurst in Victoria, Australia, an instrument which marked a significant advance upon all preceding methods. This instrument, called a clinostat, consisted of a glass phial, in the bottom of which was a compass needle and in the top a small glass plummet. The phial was filled with hot transparent gelatin and lowered into the well. The density of the plummet and of the float supporting the needle was designed in such a way that they both would float freely in the hot gelatin.

SUMMARY The oz1 ive11 surveyinq ran he carried out by means of the multiple shot instrument or the sinqle shot instrument. The srrond type instrument is Maqnetic. It is possible to pump Criell? 'I he tidvantages o this type of instrument are those earlier pioneers, it was Americian talciit that ihat il can be run in either cased or open holes with reduced their experience into tools and rriethotls universally sntisfador results and To date, its one great disadvan would oiperate with a minirnum simplicity and operating is its 5iie-beiiig too large to safely run in six-inch tirne, as well as expense. Its delicate mechanism requires tlie most therefore, will be confined to a disrussion of those instauments careful treainieiit aind, in ninny instances, when the and tools now in wide Lise in the American roiiditian oí ihe hole is doubt ul, a dummy run is first fields, and of those sppliralinns nnd advantages which made withoiit the instiiiment to ascertain the degree of make the practice so popular.

ABSTRACT The author first discusses briefly the value of constant surveys to determine verticality of well bore; then discusses controlled directional drilling, how accomplished, and where used. The purpose of this paper is to bring out the importance of well surveying and the economic applications of directional drilling. In fact, the two are so closely related that to discuss one necessarily includes the other. Years ago, the only persons giving much thought to the verticality of oil wells were the geologists who were sometimes distressed over the lack of uniform correlation, and production men who reasoned that the excessive weal on rods and tubing might possibly be due to their being in a crooked hole. This, added to some spectacular twist-offs and other drilling worries, resulted in an extensive engineering study, of crooked holes and their causes, which in turn led to the now almost universal practice of conducting some type of verticality surveys during the course of drilling. The objective is now a vertical hole. Until recently, the only economical means of judging the degree of verticality has been through the use of such recording methods as the acid bottle, the ink syphon, and a number of plumb-bob devices which pricked on a concentrically-ringed disc the number of degrees a well was off vertical. A well that remained within 3 deg. was, and is now, considered a reasonably vertical hole; if over 3 deg., it was probably plugged back to the point of excessive deflection and straightened. The angle at which a well is drilling is most often regarded more as a figure, a quantity to stay within, like the red line on the weight indicator, and not in its trigonometric sense where the degree of inclination is directly related to the number of feet the bottom of the hole will be away from the center of the derrick on the ground. Not a great many people have taken time to figure that a well which is within 2 deg. or 3 deg. of vertical for 5,000 ft. can have its bottom from 175 ft. to 261 ft. away from the point where it was spudded in at the surface. The earlier surveying methods failed to show these facts. The operator had no indication of the direction; he had only an unrelated quantitative measure. The deviation as indicated by this series of vertical angles might be cumulative in any direction along a line radial from the derrick; it might be along a spiral, or it might reverse upon itself; the actual course of the hole was impossible to determine without elaborate orientation of the drill pipe. That holes do so wander around is common knowledge, and has in the past been illustrated by such competent observers as Lahee, Anderson, Judson and Murphy, and many others. Directional surveys were mostly taken after the well had reached its total depth; and besides being rather expensive, the survey showed only the results of the drilling operations. Without using this expensive method from time to time during the course of drilling, the final location of the bottom came as a surprise, and often an unpleasant one.