Real time monitoring of drilling operations has added value and with increasing cost per foot of well bores due to their complexity it makes real time monitoring of drilling operations a key element of drilling cost reduction. With the emergence of rig sensors, WITSML, and the capturing of data with MWD systems, the industry is actively working to increase the utilization of real time data to support drilling decisions in control rooms and real-time operation centers (RTOCs). One of the main purposes of these data centers is to support drilling teams in their decision-making process.
The ability to detect drilling dysfunctions immediately helps to prevent catastrophic failures of BHA components, to reduce NPT and to increase on-bottom time. Up to now, drilling dynamics problems such as stick-slip, bouncing or whirl required downhole data for timely mitigation. However, the collection of downhole data required the usage of expensive data recorders that represented an additional cost and an additional risk of BHA problem. Thanks to the increase of the volume of data collected by mud logging companies and the development of sophisticated algorithms, Varel has developed a drilling dysfunction detection method using only surface data. It is called DrillPerf.
A DATA AGGREGATOR
DrillPerf is a software program that provides real-time decision support using only surface data which are retrieved from a Well Information Transfer Standard Makeup Language (WITSML) server. The software can be deployed in several configurations (figure 1) to support decision making onsite and offsite so that few or all can view the output.
Decisions are supported through analyzing real-time data streams of parameters measured only on the surface. The patent pending algorithm packaged into DrillPerf combines several years of scientific research and field proved models on drilling dynamics, drill bit behavior and drilling performance assessment in various drilling environments. The algorithm is based on the combination of proprietary criteria such as drilling energy (the torque component of the drilling performance criterion), drilling strength (the weight on bit component of the drilling performance criterion) and drilling impedance (the formation intrinsic resistance to bit penetration).
Figure 1: Software deployment options
DATA INPUT AND OUTPUT
The software contains capabilities to connect to the WITSML server, to clean and correct raw data, then estimate drilling performance, formation change, bit balling, bit wear and vibrations that are sorted into torsional vibrations, lateral vibrations and axial vibrations. The software requires real time data at a sampling rate of 0.2 to 1 Hz i.e., one data point each 5 seconds to one data point per second. The time base required parameters are:
- Measured depth,
- Bit depth
- Bit RPM (if a downhole motor or turbine is used)
- Hook load,
- Rotary torque
- Flow rate.
When the software is calibrated at the rig using local data of current drilling practices and with basic drill bit attributes such as bit size, cutter size, blade count and average rake angle; DrillPerf can be started and runs with input from rig sensors to be able to detect drilling dysfunctions. Comparative studies showed a great accuracy between downhole measurement using MWD/LWD data and drilling dysfunctions detected with the DrillPerf software using exclusively surface data.
The output (figure 2a and figure 2b) are presented into a log track format that includes input data used to process drilling performance variables such as mechanical specific energy (MSE), drilling impedance (DRIMP), drilling strength (S). These criteria are used to characterize drilling dysfunctions such as torsional vibrations (slip-stick), axial vibrations (bit bounce), lateral vibrations (bit whirl). Drilling dysfunctions are displayed in traffic light format: Green - no dysfunction, Orange - moderate dysfunction, and Red – severe dysfunction that requires driller attention.
Minimizing vibrations is important to mitigate the damage of bit and BHA components that lead to reduced ROP and unnecessary trips. The real time analysis identifies symptoms of problems, which are highlighted Orange and provide best practices for how to handle the current situation. Total dysfunctions are displayed in Red while curing solutions are provided in the recommendation panel.
Figure 2a: Output display
Figure 2b: Drilling Dysfunction indicators in the alarm panel
The key objective of the post run analysis is to identify optimal drilling parameters to maximize drilling performance and to provide the driller with a roadmap of optimal drilling parameters. To achieve this objective, data are aggregated and analyzed on vertical depth basis to set correlation between formations and wells (figure 3a and figure 3b). Cross plot analyses are performed by combining the target of increasing ROP and minimizing drilling energy with the target of reducing drilling dysfunction. Combinations of drilling parameters which lead to lower energy and higher ROP without dysfunction are analyzed in the example shown in figure 4. In this case, the optimal WOB ranges between 20 to 28 klb and the optimal RPM ranges between 136 to 144 RPM produce the best results. This analysis can be performed at the section level or by formation. Table 1 shows a typical example of a roadmap built for a given bit type by formation and the roadmap provides the range of optimal WOB and RPM to be applied for reaching the maximal possible ROP while minimizing drilling dysfunctions.
Figure 3a: Overview of a well, input parameters on the left and output on the right
Figure 3b: Drilling parameters and drilling performance sorted by formation
Figure 4: Drilling Parameters cross plots
Table 1: Optimal Drilling Parameters Roadmap
CASE STUDY: SUCCESSFUL IMPLEMENTATION IN THE NORTH SEA
DrillPerf has been deployed in North Sea to monitor three sections of 17 1/2” drill bit runs, four sections of 12 1/4” drill bit runs, and three sections of 8 1/2” drill bit runs in an HPHT drilling environment. The monitoring was conducted from April 2017 to May 2018 representing cumulatively over 200 days.
Thanks to DrillPerf and the lessons learned during the drilling campaign, the overall performances in all the three sections were improved. The table below summarizes the improvement made in the 12 1/4” section from the first well considered as reference to the third well. The average ROP was increased on the second and third well with one additional trip. The fourth well combined an increased ROP and a minimum number of trips.
The overall savings on the 12 1/4” section is estimated at £500,000.00.
Drilling dysfunction can be mitigated with proper selection of drilling parameters, but effective drilling decision making will require real time reliable dysfunction indicators available to the driller. DrillPerf provides these indicators on the rig floor and in duplicate to remote locations. The software is cost effective since it operates with only surface data and is user friendly thanks to the traffic light system used to alert on dysfunction. Post run analyses lead to the establishment of drilling roadmaps for optimal drilling parameters selection for future wells.
For more informaiton, please contact Alfa Dourfaye at email@example.com