Behrad Rashidi

New Approach in Real-Time Bit Wear Prediction

Challenging wells have been drilled recently utilizing advanced real time tools and techniques to optimize drilling operation while reducing risk and increasing safety. Moreover, the real time tools and techniques help identify upcoming drilling problems using real time data before they occur. Real time drilling analysis begins when real time drilling data are available and transmitted to the office locations via a remote server. The data can then be interpreted and analyzed by the engineers implementing various models for appropriate decision making. Lately, real time bit wear estimation has been a challenge in drilling a well to reach to the highest drilling performance and avoid bringing serious problems to the bit. It has been shown that the combination of Mechanical Specific Energy (MSE) and drilling rate models can be used for real time bit wear estimation while drilling. As MSE does not take the bit wear effect into account while drilling rate or rate of penetration (ROP) models do, their difference can be used to monitor and identify bit wear status while bit is in the hole. This paper demonstrates a new form of a developed model to predict bit wear status while drilling which is built by combining rock energy (MSE) model with a newly developed drilling rate model for roller cone bits as well as a previously developed model for PDC bits. Rock confined compressive strength (CCS) is obtained from ROP models and used in conjunction with MSE values to predict bit wear trend. Several bit run sections from offset wells in Alberta, Canada were tested utilizing the model and final results are compared with the reported bit wear outs from the field. Encouraging results show that this methodology can be applied to detect changes in drilling efficiency by monitoring bit wear trend in real time while drilling. Introduction Large portion of the drilling cost is related to non-productive time which is associated with drilling problems . Although there has been a great attempt to address drilling problems in real-time while drilling using various tools and techniques, they are still challenging to be identified and hindered. Bit wear is one of the main causes that affect drilling performance. This work aims to employ more comprehensive ROP models combined with the MSE model through a developed methodology to predict bit wear especially in real time while drilling . A previous methodology was established based on using Burgoyne and Young ROP model for both rollercone and PDC bits which shows uncertainties for the calculated results. In this study, more advanced ROP models were used which integrate the effect of all the associated drilling and bit design parameters to calculate rock confined compressive strength that can then be utilized in conjunction with MSE model for bit wear estimation. The ROP model for roller cone bits was

Drilling-Derived Rock Strength Can Simulate Upcoming Well Performance

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 wells 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 wells 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. Introduction The rig cost is a major part of an overall drilling cost. Rig cost depends on the drilling time used to rotate the bit, connections and tripping in or out of the well. The use of the drilling cost equation is useful in finding the better solutions of drilling optimization. The calculation of cost per meter is done by the following conventional cost equation: ......................................................................................................... (1) D C C t C t t t C b m r r c t r f ∆ + + + + = ) (