GEODYN: A Geological Formation/Drillstring Dynamics Computer Program
- J.A. Baird (Sandia Natl. Laboratories) | B.C. Caskey (Sandia Natl. Laboratories) | M.A. Tinianow (Sandia Natl. Laboratories) | C.M. Stone (Sandia Natl. Laboratories)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 16-19 September, Houston, Texas
- Publication Date
- Document Type
- Conference Paper
- 1984. Society of Petroleum Engineers
- 5.9.2 Geothermal Resources, 1.10 Drilling Equipment, 1.6 Drilling Operations, 5.3.4 Integration of geomechanics in models, 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 1.5 Drill Bits, 1.6.1 Drilling Operation Management, 1.4.4 Drill string dynamics
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This paper describes the initial development phase of a finite element computer program, GEODYN, phase of a finite element computer program, GEODYN, capable of simulating the three-dimensional transient dynamic response of a polycrystalline diamond compact (PDC) bit interacting with a non-uniform formation. The ability of GEODYN to simulate response variations attributable to hole size, hole bottom surface shapes, and formation material non-uniformities is demonstrated. Planned developmental phases will address the detailed response of a bottom-hole assembly (BHA), a drill ahead (rock penetration and reinoval) simulation, and ultimately, the response of the entire string.
GEODYN is a finite element computer program being developed in concert with an advanced drilling system under the auspices of Sandia National Laboratories Geothermal Technology Development (GTD) Program. The major goal of these efforts is a reduction in the costs associated with drilling geothermal wells. One element of the Program concerns itself with the design and fabrication of both electronic and hydraulic downhole components which will be used in the drilling system. These drilling components will be required to function under severe downhole environmental conditions such as mechanical shock and vibration, temperature, etc. Another element of the GTD Program is the development of the GEODYN computer Program is the development of the GEODYN computer program. This computer program will function in two program. This computer program will function in two interrelated capacities. First, the program will be used to simulate the dynamic response of the bitdrill string assembly during the drilling process to aid in the design of "hardened" electronic and hydraulic components. Secondly, GEODYN will be utilized to simulate the drilling process itself which includes rock penetration, bit torque, side forces, hole clearance considerations, bottom-hole assembly response, directional tendencies, and drilling rock formation interfaces. This paper will demonstrate GEODYN's ability to simulate the drilling process.
The use of computer programs to aid in the analysis of bottom-hole assembly response became an accepted technique in the seventies. The modeling techniques have now been extended from simple two-dimensional static modeling to three-dimensional steady state dynamic simulations. These computer programs, usually, utilize a drill string idealization consisting only of beam type finite elements. As such they share an avowed inability to accurately account for intermittent non-uniform bit cutter formation interaction as well as formation penetration effects. The GEODYN development program is based on a desire to characterize such complex, nonlinear, intermittent interaction between a rotating PDC bit and materially non-uniform irregular bottom hole formations. The GEODYN Phase I program is written in FORTRAN 77 and has been installed on both a VAX 11/780 and CRAY 1 computers.
This paper first outlines the modeling approach adopted to simulate complex interaction of this type. A brief review of: (1) the bit-drill string model; (2) the incorporation of a "ghost cutter" idealization to model each and every PDC cutter, gauge cutter, and wear button; and (3) the characterization of the non-uniform, irregular down hole formation(s) with a "discrete point" model is presented. The implementation of a dynamic solution algorithm employing a modal reduction procedure is also introduced. When coupled, these techniques and procedures have permitted the detailed modeling of the permitted the detailed modeling of the bit-formation(s) interaction in a very efficient manner. Next, a series of verification problems are presented. Penetration, bit torque, side force and bit presented. Penetration, bit torque, side force and bit motion responses associated with variations in hole size, hole shape, and formation properties are reported. The observed response and differences in the results attributable to the modeling variations are discussed. These results indicate that GEODYN will provide a valuable aid in simulating both drilling provide a valuable aid in simulating both drilling behavior and the drill string response.
|File Size||1 MB||Number of Pages||9|