True Vertical Depth

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  1. PROGRAM HELPS QUICKLY CALCULATE DEVIATED WELL PATH

    Mark P. Gardner Plains Resources Inc. Houston A Basic computer program quickly calculates the angle and measured depth of a simple directional well given only the true vertical depth and total displacement of the target. Many petroleum engineers and geologists need a quick, easy method to calculate the angle and measured depth necessary to reach a target in a proposed deviated well bore. Too many of the existing programs are large and require much input data. The drilling literature is full of equations and methods to calculate the course of well paths from surveys taken after a well is drilled. Very little information, however, covers how to calculate well bore trajectories for proposed wells from limited data. Furthermore, many of the equations are quite complex and difficult to use. Fig. 1 lists a computer program with the equations to calculate the well bore trajectory necessary to reach a given displacement and true vertical depth (TVD) for a simple build plan. It can be run on an IBM compatible computer with MS-DOS version 5 or higher, QBasic, or any Basic that does not require line numbers. QBasic 4.5 compiler will also run the program. The equations are based on conventional geometry and trigonometry. EQUATIONS The equations are derived from the well bore distances and angles shown in Fig. 2. The variables used in the equations are shown in Fig. 2. The following subscripts are used with these variables: T = total, B = build, R = run, KOP = kick off point, and _ = delta. Equations 1-3 are simple geometric equations, and Equations 4-6 are based on standard trigonometry. The displacement and true vertical depth are then found by using geometry and trigonometry with these equations (Equations 7 and 8). With the starting angle set to zero (01 = 0, and cos O = 1), Equation 7 simplifies into Equation 9. Substituting the build displacement, DispB, into Equation 1 yields Equation 10, which is then solved for the run displacement, DispR (Equation 11). Equation 12 is derived from Equation 3 and the true vertical depth of the run (Equation 6), TVDR and the true vertical depth of the build (Equation 8), TVDB-DispR from Equation 11 is then substituted in Equation 12 to yield Equation 13. Both sides of Equation 13 are multiplied by tan 0 and rearranged to yield Equation 14, which can be simplified into Equation 15. Because Cos2 0 + sin2 0 = 1, Equation 15 can be further simplified into Equation 16. ITERATION Equation 16 cannot be solved by further reduction; the solution is obtained through iteration. The equation can be solved by rearranging terms and iterating the angle 0 until Deltaerr is within acceptable tolerances, or as close to zero as practical (Equation 17). Engineering judgment must be used to decide the acceptable tolerances for each well. Because this equation requires an iterative solution, the first guess should be assumed to be between 90 (upper boundary) and 0 (lower boundary). The next iteration should use an angle midway between the first guess and one of the boundaries. By using the midpoint between each guess and a boundary, the function diverges quickly. Therefore, it is not necessary to take the derivative of the function. The following notes are important for running the program: The program's input angle must be in radians. Because the run, R, is conventionally given in degrees/100 ft in the oil field, this value must be converted to radians/ft (1 = p/180 radians). A first guess for the angle 0 can be estimated by ignoring the build section and taking the arctangent of the total displacement, DispT, divided by the change in true vertical depth, TVD_. Note that the top and bottom boundaries change depending on the result of each guess for the iteration. Copyright 1993 Oil & Gas Journal. All Rights Reserved.

    Magazine Articles

    Magazine Articles

    Mon, 22 Nov 1993

  2. SIMPLE PC PROGRAM CALCULATES MODIFIED S-TYPE WELL TRAJECTORY

    Abdel-Alim Hashem King Saud University Riyadh, Saudi Arabia A simple personal computer (PC) program written in Basic can quickly calculate the trajectory of a modified S-type deviated well. The program calculates the build-up angle, the measured depth, the true vertical depth of each interval, the ...

    Magazine Articles

    Magazine Articles

    Mon, 20 Feb 1995

  3. Texas-Gulf Coast: Serbin field horizontal drilling planned

    FieldPoint Petroleum Corp., Austin, and Riley Exploration Group, Blanchard, Okla., signed a joint exploration agreement to horizontally drill new wells and rework existing vertical wells in Serbin field in Lee and Bastrop counties, Tex.

    Online Articles

    Online Articles

    Wed, 27 Nov 2013

  4. Kentucky: More drilling set near Lawrence County find

    App Energy LLC plans to drill as many as five more wells by yearend near a discovery in the Twin Bottoms field area of Lawrence County, eastern Kentucky.

    Online Articles

    Online Articles

    Thu, 12 Sep 2013

  1. Cairn spuds wildcat, takes farmout offshore Morocco

    Online Articles

    Online Articles

    Mon, 28 Oct 2013

  2. WPX to develop San Juan Gallup oil discovery

    WPX Energy Inc., Tulsa, will drill 8-10 development wells in New Mexico in 2013 near a San Juan basin oil discovery at which the first four wells flowed at commercial rates from Cretaceous Gallup sandstone.

    Magazine Articles

    Magazine Articles

    Mon, 9 Sep 2013

  3. Exploration/Development Briefs

    interest and FieldPoint 25%. FieldPoint has working interests in 72 producing oil and gas wells in Serbin field, 50 miles east of Austin. Cretaceous Taylor sand produces 46° gravity oil from 5,300-5,600 ft true vertical depth .

    Magazine Articles

    Magazine Articles

    Mon, 9 Dec 2013

  4. OGJ Newsletter

    International news for oil and gas professionals

    Magazine Articles

    Magazine Articles

    Mon, 1 Sep 2014

  5. Sawn Lake SAGD project steam injection nears

    Horizontal wells are about to be spudded at a heavy oil steam assisted gravity drainage demonstration project at Sawn Lake, Alta.

    Online Articles

    Online Articles

    Thu, 3 Oct 2013

  6. Exploration/Development Briefs

    sidetracking, may be undertaken in the event of success. Malida-1 is to go to 2,670 m measured depth, 2,640 m true vertical depth , in 47 m of water in about 18 days.

    Magazine Articles

    Magazine Articles

    Mon, 25 Nov 2013

  7. Morocco: Gulfsands drilling for Rharb basin gas

    Gulfsands Petroleum PLC has spudded the Al Krima-1 well on the Rharb Centre permit in northern Morocco, the first of nine wells to be drilled in two back-to-back programs on the company’s Rharb permits.

    Online Articles

    Online Articles

    Tue, 29 Oct 2013

  8. Brunei: Noncommercial gas flows at onshore prospect

    Serinus Energy Inc., Calgary, is moving the drilling rig to its Luba well location on onshore Brunei Block L after the Lukut Updip-1 well flowed at noncommercial rates estimated at less than 50 Mcfd from a secondary objective after failing to reach its primary target.

    Online Articles

    Online Articles

    Fri, 18 Oct 2013

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