The televiewer takes an oriented acoustic picture of the inside of the well bore in the form of a continuous well log. The resulting log is a representation of the well bore wall as if it were split vertically along magnetic north and laid out flat. Both induced and natural fractures are defined in remarkable detail. Well bores can be filled with any homogeneous liquid such as lease crude oil, water, or drilling mud. Resolution of the tool is sufficient to locate fractures 1/32 inch wide. Examples of natural fractures in extremely fractured formations, in shales, and also drilling‐induced fractures are discussed. Fracture orientation information useful for local and regional tectonic studies is presented.

Zemanek, J., Mobil Research and Development Corp. Caldwell, R.L. Mobil Research and Development Corp. Glenn Jr., E.E., SPE-AIME, Mobil Research and Development Corp. Holcomb, S.V., Mobil Research and Development Corp. Norton, L.J., Mobil Research and Development Corp. Straus, A.J.D., Mobil Research and Development Corp. The Borehole Televiewer logging tool takes an acoustic picture in the form of a well log, it invaluable for formation evaluation and borehole inspection. The log, which is run continuously, can define both induced and natural fractures, and can reveal vuggy porosity, the size and distribution of perforations in casing, and casing failures. Introduction A new and unique logging tool, called the Borehole Televiewer (BHTV), has been developed to inspect boreholes and to evaluate formations. Even though geologists and engineers have had only about 3 years' experience with the BHTV, the thinking of many of them has been radically influenced by the fascinating and revealing "log-picture" recorded with the tool. The BHTV fills a need for a logging tool that can produce a direct and descriptive record of the produce a direct and descriptive record of the physical properties of the borehole environment. Although physical properties of the borehole environment. Although primarily developed to evaluate fractured reservoirs, primarily developed to evaluate fractured reservoirs, the BHTV has been used successfully to solve a variety of problems related to formation evaluation and borehole inspection. Geologists and petroleum engineers have been confounded for many years by the problems of locating and evaluating fractures. Interpretation of the usual resistivity, acoustic or radioactivity logs, as well as the analysis of cores, for evaluation of fractured reservoirs is extremely difficult and often not definitive. This is understandable since analysis of cores from fractured formations has reported variously:low porosity,no effective permeability,lack of porosity,no effective permeability,lack of any matrix oil saturation andoil stains on fracture planes as the only indications of potential production. In recent years acoustic amplitude logs production. In recent years acoustic amplitude logs have been introduced and used with varying degrees of success to locate fractures. Conventional amplitude logs at best give only qualitative answers where quantitative ones are desired. The logs reveal nothing of the orientation of the fractures. In addition to these logs, various types of cameras, television, and rubber impression packers have been used for borehole inspection. (See Appendix.)The BHTV logging tool supplies both the quantitative and the orientation answers about fractures. The borehole can be filled with any homogeneous, gas-free liquid such as fresh water, saturated brine, crude oil or drilling muds. This tool takes an "acoustic picture" of the borehole wall. The resulting log is a picture" of the borehole wall. The resulting log is a representation of the borehole wall as if it were split vertically and laid flat. The log is oriented with respect to magnetic north. Any physical changes in the borehole wall are seen as changes in picture intensity. In this way, fractures, deformation or pits are reflected on the log. pits are reflected on the log. Tool Description The fundamental parts of the BHTV are shown in Fig. 1. A piezoelectric transducer probes the borehole wall with bursts of acoustic energy. A flux-gate magnetometer senses the earth's magnetic field and provides the means for determining the orientation of the log. JPT P. 762

Multiple, vertical fractures can be created from a single, directionally drilled wellbore. The procedure increases the attainable fracture area without adding wells, and provides more rapid and efficient drainage of a specific reservoir volume. Introduction For any reservoir with a given set of conditions there should be a drilling, completion, and production procedure that will optimize the financial recovery from procedure that will optimize the financial recovery from that reservoir. This paper focuses on a procedure that should be considered for application in certain types of reservoirs. This procedure involves creating multiple, vertical fractures from an inclined wellbore and the subsequent production from the system. The effectiveness of hydraulic fracturing is well known, both from experience and from theoretical considerations. The concept of a fracture represented by an enlarged wellbore is discussed by Prats et al. The effects of fracture penetration and fracture conductivity on improvements in production are shown by McGuire and Sikora and Tinsley el al. In low-permeability reservoirs, sufficient conductivity contrast between fracture and formation can be obtained to make well productivity increase almost directly proportional to fracture length. Thus, for vertical proportional to fracture length. Thus, for vertical fractures of fixed height, productivity increase is directly proportional to fracture area. From the above discussion we can conclude that a method to increase the effective fracture area attainable is desirable. To be useful, any such method must, of course, be more profitable than the practical alternatives. For a reservoir volume element of fixed size, the maximum vertical fracture area is attained when the fracture is extended to the boundaries of the element. Additional fracture area can only be obtained by drilling and completing additional wells within the volume element. A procedure for producing several vertical fractures from a single well would increase the attainable fracture area without adding wells. Such a procedure and a field experiment to test it are presented here. presented here. The Multifrac Concept The object of this multiple fracturing process (multifrac) is to obtain greater fracture area through closer fracture spacing than could be obtained from the same number of wells with single, vertical fractures. The increase in well productivity resulting from this greater fracture area per well is not gained without penalty. Because the process requires substantial penalty. Because the process requires substantial deviation of the wells from vertical, both measured well depth and drilling cost per foot are increased when compared with a vertical well. This idea has also been suggested by Pasini and Overby. The concept is illustrated in Figs. 1 and 2. Theory predicts, and observation confirms, that hydraulically predicts, and observation confirms, that hydraulically induced fractures are generally vertical, except in relatively shallow formations. Thus, it should be possible to generate several fractures from a single possible to generate several fractures from a single deviated hole, as shown in the figures. To accomplish this, the azimuth of the deviated wells must be at a high angle (preferably 94) to the fracture azimuth. The Borehole Televiewer (BHTV) is effective for determining the azimuthal orientation of vertical fractures in a vertical wellbore. JPT P. 641

The corrosion of mild steel by a spray of dilute acetic acid solutions in an air-free CO2 atmosphere was studied. With less than 500 ppm acetic acid, the corrosion rate of steel varied inversely with acid concentration at constant partial pressure of CO2. Using 500 to 1000 ppm acetic acid, the corrosion rate was low, following initial rapid attack, and independent of the partial pressure of CO2. The corrosion rate was independent of CO2 pressure at 1 arm or below for all acid concentrations used, except the lowest, 50 ppm. At 1.5 arm CO2, a substantial rate increase was observed at all acid concentrations. The corrosion product formed in the presence of CO2 was largely iron(II) carbonate. This carbonate film offered some protection to the metal surface until it became thick enough to part because of internal stresses.It is postulated that higher acid concentrations led to the lowest continuing corrosion rate because fine particles precipitated during the rapid initial attack, and the resulting fihn on the metal was relatively less permeable to the corrosive fluids. At lower acid concentrations, the precipitate was coarser and the resulting film was more porous, leaving considerable metal surface exposed to the corrosive medium. Experiments to support this view are described.

A positive displacement-type pump in which there are no metal parts exposed to the fluids has been built and tested. Gases, liquids, or mixtures of both can be pumped without any corrosive effects on the pump.