Summary In this paper, a new drilling optimization procedure is presented that is designed to improve the drilling efficiency with positive displacement motors (PDMs) and PDC bits. This developed optimization method is based on predicting rate of penetration (ROP) from PDM outputs for any PDC bit design. More specifically, optimization is done for a hole section and optimum values of weight on bit (WOB) and surface RPM are obtained for the section. For given flow rates, estimated values of optimum WOB and surface RPM are used to calculate the corresponding motor differential pressures and the foot by foot ROP values. Also, the method is used to show how improper operational parameter selection can affect total drilling time. A case study was done to consider different PDMs with different lobe configurations and a set of fixed operational parameters. The presented method is verified by generating a confined rock strength log based on drilling data for a previously drilled well in Alberta. This foot-by-foot strength log is compared to a confined rock strength log generated as a follow-up analysis by a commercially available drilling simulator package. Also, a PDM differential pressure log is generated and compared to field-recorded on-bottom differential pressure values. The method's application is best demonstrated by simulating the drilling operation of the Alberta well with three different PDMs. It is shown that consideration of PDM performance/selection in the drilling planning phase will help to perform a safe and cost-effective operation by preventing motor stalls and maintaining highest average ROP for the section. It is also shown that by optimizing WOB and surface RPM values for a constant mud flow rate and predefined bit wear at total depth, a maximum average ROP for the section can be reached for any PDM.

Bearing failure of roller cone bits may result in a time-consuming fishing job, and lead to significant increase in drilling costs. The bearing failure generally comes from over wear of frictional pairs (surfaces between the journal and bearing of the cone). A bearing wear model has been developed to predict the wear status through multi-variable nonlinear regression analysis based on field data. The wear model considers four variables including weight on bit (WOB), revolution per minute (RPM), diameter of bit and hours drilled as a function of IADC bit bearing wear. Some abnormal bit run field reported bearing failures were removed in order to acquire the best regression of the field data. A bearing failure probability model is then introduced to predict the survival probability of the bit, the parameter of which is obtained through statistics of more than 500 bit runs. The wear status, including instantaneous and cumulative wear, for different roller cone bits and different wells drilled in Western Canada is simulated respectively with the wear model. A good correlation coefficient was obtained for different IADC bit types including both milled tooth and insert roller cone bits. The cumulative wear values from the model match close those from the field. The wear model and the failure probability model can help drilling engineers evaluate bearing wear status during real time drilling operations through simulation, and make a decision on when to pull out the bit in time to avoid bearing failures and the possibly lost cones. Better bearing wear predictability will result in better drilling results and effect the total drilling cost.

The Wellsite Information Transfer Standard Markup Language (WITSML) is a global open standard for the exchange of geotechnical data in the upstream oil and gas industry.Saudi Aramco has embarked upon a project to implement the transfer and storage of all wellsite real-time data using the latest released WITSML specification. This project is called the Real-Time Data Transmission and Viewer Service (RTDTVS). Through this project the data from all rigs will be captured and transmitted back to the Drilling Real-Time Data Hub (DRTDH), which runs on an Oracle platform with triple redundancy.Drilling sensor data has not in the past been transmitted back for monitoring purposes; instead, Saudi Aramco has previously left the drilling contractor to manage the drilling process. On exploration wells a mud logging contractor is often used, and real-time data has been available to the different asset teams; but on development wells, a mud logging contractor is not used, making the need to capture the drilling sensor data vital not only for safety monitoring, but also for the optimization of the drilling process to reduce well drilling costs.To make accurate calculations of drilling performance indexes it is necessary to have access to some information that is typically not transmitted as part of a real-time data stream, but is available instead through daily reporting and other mechanisms. This paper discusses how the use of the WITSML Open Standard has enabled drilling sensor data stored in the DRTDH to be integrated with report data available through the Saudi Aramco Drilling Knowledge Database (SADK) to provide more efficient and safer drilling practices. IntroductionWITSML is a continually developing open standard for the transmission of real-time, historical and contextual drilling and completions information.

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This paper describes the continued and increasing impact of the Wellsite