Finding the Optimum BHA through Data Analytics & Modeling Brandon Cherry

Outline Introduction BHA Modeling Data Case Study-Post Analysis Description of the Model Rock-Bit-BHA coupling Bit Steerability Vibrations Data TFO efficiency WOB Hole Overgauge Case Study-Post Analysis Curve Lateral Conclusion

Introduction The methodology proposed in this presentation shows an effective way to analyze post run data and to understand and predict downhole behavior: The Drilling Bit Characteristics Steerability (Side cutting ability) Walking tendency (Turn rate) The Rock Formation: Hardness (UCS) Anisotropy (Dip angle) The Directional System: Rotary Steerable System (RSS) BHA Rotary Steerable Mud Motor With/Without Reamer Capability The methodology proposed in this presentation shows an effective way to analyze post run data and to understand and predict downhole behavior: The three main factors that we consider are the bit characteristics, the rock formation, and the directional system. (State each bullet point)

(Deflection, Tilt, Bending Moment, Contact Forces) Bit-Rock-BHA Model Rock-Bit Model BHA Model + + = (Deflection, Tilt, Bending Moment, Contact Forces) We’ve found that combining a BHA model with a detailed bit/formation model can maximize an engineer’s understanding of the interaction between the rock, the bit, and the BHA.

Bit Steerability & Walk Turn Rate Build/Drop Rate High Bit Steerability = High Side-Cutting ability of the bit Bit Steerability = 5 - 40% for most PDC Bits Bit steerability is defined as the side-cutting ability of the bit and attributes to build and drop rates The bit walk angle is the angle between where the side force is applied and the direction of deformation. This attributes to turn rates.

Effective Gauge Length Bit Steerability Effective Gauge Length Lab Results Model Bit Steerability (%) Gauge Length (in) It’s important to understand the effect that gauge length can have when considering a bit. We can see here that lab tests show that an increase in gauge length decreases bit steerability and vice versa for a short gauge bit.

Bit Tilt Theory This slide shows us the differences between long gauge and short gauge bits. A longer gauge bit will naturally want to drill in the direction of the system’s tilt. While the shorter gauge bit will want to drill into the direction of the side force. Formation characteristics also play a large role in drilling behavior (Next slide).

Bit Steerability vs. Rock Formation Effect of Rock Hardness We can see that if we have the same bit and same BHA, it’s still possible to not get the same build rates. This is due to potential differing formations and rock hardness. The bit steerability drastically drops as we transition from a soft formation to a hard formation. It’s extremely important to know the UCS of the formation you are drilling to improve efficiency.

Vibration Modal Analysis • The evaluation of critical RPM based on resonant frequency of the BHA • Torsional and Axial Nodes – Dependent on entire Drill String – Dependent on Stiffness/Mass – Easy to plan for in advance and apply across several wells/fields • Lateral Node – Dependent mainly on BHA & Well Path – Sensitive to WOB & Hole Overgauge

Data Quality BHA Details Drilling Parameters (i.e. WOB) Bit Characteristics Motor/RSS Specifications String Diameters Stabilizer Placement Drilling Parameters (i.e. WOB) Toolface Orientation & Slide/Rotate Length (Raw Data vs. Slide Sheet) Rock Formation Hardness (UCS) Mention each bullet point.

Bottom Hole Assembly Having a detailed and accurate BHA is crucial when trying to understand and predict the drilling behavior down hole. This is an example of a detailed BHA input with accurate OD’s, ID’s, and contact points in the wellbore.

Tool Face Tendency Planning ahead for Slide Efficiency & Slide Time is key for designing your BHA build rate requirements Toolface Control Reactive Torque Formation deflections Slide vs Rotate % of time sliding vs rotating 0° 15° 30° 45° When trying to build the optimum BHA for build rates, some trend analysis should be done from offset wells or known formation tendencies. Knowing this information will help you to predict reactive torque and possible formation deflections. It’s also critical to plan the percent of time sliding vs. rotating as switching back and fourth can create some tortuosity/micro doglegs in the wellbore. This figure shows us the build and turn rates calculated for a steerable mud motor at different toolface orientations. (Elaborate on graph).

Slide Sheet vs TFO Data Discrepancies in slide sheets vs. actual toolface orientation can be detrimental to the accuracy of post analysis. Slide Sheet = 340 deg Avg. Raw TFO = 324 deg Discrepancies in slide sheets can be detrimental to the accuracy of post analysis. With a constant 340 deg TFO for the entire stand, an assumption has to be made that there is no tortuosity present and we have a perfectly smooth borehole. However, looking at the EDR data, we can see that due to possible reactive torque or deflections, there are fluctuations in the TFO. This leads to tortuosity being present.

Weight on Bit The WOB applied during drilling operations has a major effect on modeling Deflection and contact points can change according to the level of compression WOB (klbf) Inclination (deg) Build Rate (deg/100 ft) 20 10 15 30 16.6 Accurate WOB data is also very important when it comes to modeling and predicting BHA behavior. This particular study showed that at the same inclination, applying more WOB would increase the build rate by almost 2 degrees.

Hole Overgauge The larger the hole overgauge, the more likely you wont achieve your build rates Much like WOB, the presence of Hole Overgauge can result in drastically different build rates than what was originally predicted. We can see here that the difference in 0 and 1 inch hole overgauge led to a drop of almost 5 degrees in build rates. Putting all of this information and data together allows us to build strong models and ultimately gain a better understanding of the formation we are drilling, as we’re about to see in the next slides.

Case Study – BHA Post Analysis Methodology Designed an optimized BHA by: Observing the results of a steerable mud motor BHA that drilled in multiple formations in the curve and lateral Collecting accurate post run data from the field Defining or zoning specific areas for segmentation Performing a sensitivity analysis on hole overgauge, bit steerability/walk, and friction factor

Case Study – Data Segmentation Input: Actual Surveys Run Interval & MW Actual BHA WOB Log TFO Log Activation Level Calculating: Activation % Average TF Average WOB User Selected: Intervals based on similar trend, RSS Activation, Inclination, Formation, etc After obtaining data from the field, specific zones or segments were created to isolate trends and behaviors.

Case Study – Data Segmentation Next, a sensitivity analysis was performed in order to match the model’s predicted behavior to what actually occurred. This is done by adjusting bit steerability, walk, and hole overgauge.

Post Analysis – Curve Section Actual Build Rates (Red Lines) vs Predicted/Calibrated Build Rates (Green Squares) The results of the case study showed that the two formations in the curve section had very different hole overgauges, which lead to lower build rates in one vs. the other.

Hole Overgauge – Curve Section First contact point shifted from sleeve to motor bend when Overgauge increases from 0.25in to 0.75in The model showed that while drilling with a smaller overgauge, build rates were sustained due to the contact point on the motor being on the sleeve. The contact point then shifted to the motor bend when drilling with the larger overgauge, which lead to the drop in build rates.

Post Analysis – Lateral Section

Rotating Tendency – Lateral Section BHA Rotating Tendency @ 90 degree Inclination – Effect of WOB & Bit Steerability In this case, we noticed that at around 15% bit steerability, the effect of WOB was much less and the build/drop rate was within +/- 20 deg/100ft. One suggestion to improve this BHA was to slightly increase the gauge length of the bit to reduce the bit steerability. The calibration performed in this case study allowed us to

Conclusions Coupling Bit, Rock and BHA models effective for understanding directional behavior Case study allowed the determination of UCS, hole overgauge, and ultimately, an optimized BHA design for the next well

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