Drilling-Derived Rock Strength Can Simulate Upcoming Well Performance

Abstract

A drilling simulator has been used during the past four years to improve the drilling performance in Western Canada. Rate of penetration improvement and subsequent cost and time reductions are the key elements for drilling these wells. A drilling simulator is required to generate the "Apparent Rock Strength Log" (ARSL) using available offset well data. The ARSL calculation is based on using inverted Rate of Penetration (ROP) models for different bit types, reported bit wear, lithological information and pore pressure in addition to the drilling parameters. The generated ARSL can be modified and correlated for different and new formation tops for planned wells. The obtained ARSL logs for the wells in the same field have shown an acceptable overlay for the common lithologies using different bit runs and drilling parameters. Furthermore, it can be shown that the ROP match with the new simulated ROP in the same well applying another well's drilling parameters once their ARSL are adjusted. It has been shown that a typical cost reduction can be achieved for the planned wells utilizing the drilling simulator when previously drilled wells exist. The effect of using the combination of different bit runs and drilling parameters can also be explored through use of the simulator. In this paper, a study was conducted for two wells in an Albertan, Canada field to investigate the effect of using the bits used in a well to reduce cost and optimize the next well. The ARSL logs of two wells were separately obtained and compared. The comparison between the new simulated ROP for the first well, using another well's drilling data, and the available ROP for the second well is also discussed. Final results are showing an acceptable match obtained for ROP values as well as for the corresponding drilling time and final bit wear status in each of the bit run sections. Utilizing the simulator in these type wells shows a significant cost and time reduction potential and can be helpful to apply in preplanning analysis for new wells to be drilled using previously utilized bit types and designs.

An Integrated Approach for Drilling Optimization Using Advanced Drilling Optimizer

“…Generation of the bit file includes information such as bit size, depth in/out, bit wear in/out, and number/size of nozzles. In addition, since PDC bits are being used in the simulation, cutter specifications including number/size of cutters, back-rake/side-rake angle, number of blades, and junk slot area were also needed [14]. The optimizer predicts drilling performance and bit wear for each bit based on their design specifications [11].…”

“…Each acceptable range is defined by standards set by the rig, equipment, or personnel to ensure equipment is being used to their designed parameters and that safe drilling practices are being followed at all times. When data points did not fall within the acceptable range they were removed and the data was averaged between the last closest acceptable data points [14].…”

“…In order to generate the lithology file, the top depths and lithologic descriptions were input for every formation encountered when drilling the reference well. The necessary data can usually be found from geology reports or generated based on log properties [14]. Mud logs are a good data source since they record lithologic percentages of the cuttings along with relevant mud properties for every foot of the drilling operation.…”