BOP Ram Sensing and Interface Concept Rationale Intelligent BOP RAM Actuation Sensor System 11121-5503-01 November 10, 2014 Emad Andarawis GE Global Research One Research Circle Niskayuna, NY 12309
LEGAL NOTICE This report was prepared by GE Global Research as an account of work sponsored by the Research Partnership to Secure Energy for America, RPSEA. Neither RPSEA members of RPSEA, the National Energy Technology Laboratory, the U.S. Department of Energy, nor any person acting on behalf of any of the entities: a. MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED WITH RESPECT TO ACCURACY, COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN THIS DOCUMENT, OR THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS DOCUMENT MAY NOT INFRINGE PRIVATELY OWNED RIGHTS, OR b. ASSUMES ANY LIABILITY WITH RESPECT TO THE USE OF, OR FOR ANY AND ALL DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS DOCUMENT. THIS IS AN INTERIM REPORT. THEREFORE, ANY DATA, CALCULATIONS, OR CONCLUSIONS REPORTED HEREIN SHOULD BE TREATED AS PRELIMINARY. REFERENCE TO TRADE NAMES OR SPECIFIC COMMERCIAL PRODUCTS, COMMODITIES, OR SERVICES IN THIS REPORT DOES NOT REPRESENT OR CONSTIITUTE AN ENDORSEMENT, RECOMMENDATION, OR FAVORING BY RPSEA OR ITS CONTRACTORS OF THE SPECIFIC COMMERCIAL PRODUCT, COMMODITY, OR SERVICE. 2
Abstract: The sensing and interface concept rationale document provides the summary of the sensing system requirements and evaluation criteria for BOP ram instrumentation, sensor system operating concept and feasibility assessment, sensing system risk analysis and initial system specification based on risk assessment. 3
Signature and Date Stamp November 10th, 2014 Emad Andarawis, Principal Investigator Date 4
THIS PAGE INTENTIONALLY LEFT BLANK 5
Contents Table of Figures... 7 Table of Tables... 7 Table of Acronyms... 8 Introduction:... 9 Section 1: Sensing system requirements and evaluation criteria... 9 Section 2: sensor system operating concept and feasibility assessment.... 10 Sensing system operating concept:... 10 X-ray sensors operating concept... 11 EM sensors operating concept... 11 Ultrasonic sensors operating concept... 12 Section 3 Risk analysis results... 14 Summary of risk evaluation... 14 Power consumption:... 14 Marinization capability:... 14 Position sensitivity:... 15 Pipe movement:... 15 Sensor health:... 15 Capability of integration in BOP:... 15 Measurement in drilling mud:... 16 Section 4: System configuration based on risk assessment... 17 Sensor system configuration:... 18 Summary and conclusions:... 20 6
Table of Figures Figure 1 Envisioned BOP sensing concept... 11 Figure 2: X-ray approach for measuring drill pipe diameter from outside of BOP wall... 11 Figure 3 Electromagnetic sensing concept... 12 Figure 4 Ultrasonic measurement approach... 13 Figure 8: Overall system mechanical integration approach... 18 Figure 9: EM sensor receive chain block diagram... 19 Figure 10: UT sensor receive chain block diagram... 20 Table of Tables Table 1: List of sensing system requirements... 9 Table 2: Risk analysis results for the various sensing techniques... 17 Table 2: EM sensor risks and mitigation approach... 17 Table 3: UT sensor risks and mitigation approach... 17 7
Table of Acronyms BOP UT EM KSPS SPS OBM SNR ECI WBM Blow Out Preventer Ultrasonic Transducer Electro-Magnetic sensor Kilo-samples per second Samples per second Oil Based Mud Signal to noise ratio Eddy current Instrument Water Based Mud 8
Intelligent BOP RAM Actuation Sensor System Sensing and Interface Concept Rationale Introduction: The sensor integration concept rationale is divided into four sections. Section 1 covers sensing system requirements and evaluation criteria for BOP ram instrumentation Section 2 covers the sensor system operating concept and feasibility assessment Section 3 will present a summary of the risk analysis Section 4 covers the recommended system configuration based on risk assessment Section 1: Sensing system requirements and evaluation criteria The BOP un-shearable sensing system is intended to provide a means of detecting the presence of outof-range geometries. The sensing system must be robust to a number of error sources for example drill pipe movement and location. Since the sensor is expected to detect the pipe diameter even while the drill pipe is rotating, the sensor system must be robust against motion artifacts. Table 1: List of sensing system requirements Parameter Target Sensing system response time 1 seconds Senor bandwidth 5 Hz Power consumption Less than 50 watts Cavity size Compatible with 19" BOP size Effect of pipe motion Insensitive Effect of pipe position Insensitive OD measurement Range 2 3/8 18 1/2 Resolution in detecting diameter change +/- 0.1 Resolution in diameter reading +/- 0.1 Capability to detect pipe thickness Not needed Drilling fluid Oil, water and synthetic based muds, and brine Communication data rate (on MUX cable) Less than 1K bits per second Temperature range of electronics -20C to +70C Electronics packaging 1 atm. housing, 15,000PSI environment Temperature range of sensor -20C to 175C Placement Close as possible to BOP 9
Based on the requirements, a number of evaluation criteria were devised for comparing the performance of the various sensing systems envisioned. The criteria are summarized in table 2 Criteria for evaluation Power consumption Marinization capability Insensitivity to pipe position Insensitivity to pipe movement Ability of sensing system to determine the health of the sensor Capability of integration in BOP Measurement capability in drilling fluid Sensor signal conditioning and processing requirement Each of the envisioned sensing techniques was evaluated based on the above criteria and a tradeoff was conducted to arrive at the envisioned sensing system configuration. Section 2: sensor system operating concept and feasibility assessment. Sensing system operating concept: The sensing system is expected to be used by the operator as an additional validation step against the pipe length and joint location tally books that the operators currently maintain. This can assist in reducing human error in the recording of such data, and to act as backup and supplemental information to the operator. Additionally the sensing system can validate the operator s pipe stress/stretch calculations currently utilized to estimate location of pipes and joints in the BOP in the presence of elongation across the length of the pipe. Discussions with the project s working group validated the approach that the sensing system will not inhibit a shear operation from occurring and will not be used as a safety critical system. Subsequent revisions in the system may include tighter integration with the control system, and possible decision making capability, but that is outside the scope of this work. Since no autonomous actions are taken based on the sensor system, the sensor outputs are not tied to the existing BOP control system except for utilizing the same communication channels for communicating the sensor data to the user. In order for the sensing system to perform the required functions, the system must be capable of detecting changes in the pipe diameter and communicating this information to the user. Additionally, detection of absolute pipe diameter, while not required to provide the data needed to validate the information in the tally book, is desired as additional confirmation, and provides a higher level of utility to the user. An overall sensing concept is shown in Figure 1. 10
Figure 1 Envisioned BOP sensing concept X-ray sensors operating concept The x-ray sensing approach utilizes and x-ray source that generates x-rays that travel across the BOP annulus through the drilling fluid and drill pipe. Since the attenuation of x-rays is substantially higher in metal, x-ray absorption causes the drill pipe to cast a shadow on an x-ray detector. The width of the shadow is proportional to the width/diameter of the pipe. Figure 2 shows the overall x-ray measurement approach. Figure 2: X-ray approach for measuring drill pipe diameter from outside of BOP wall EM sensors operating concept 11
EM sensors utilize electromagnetic field coupling with tubular contents to detect a tool joint or other un-shearable tubular features that are in the path of a shear ram. Electromagnetic coupling is dependent on the distance between the sensor and the target. This sensor detects a change in the tube diameter over the tool joint by detecting the change in energy coupling. Figure 3 shows the overall EM measurement approach Figure 3 Electromagnetic sensing concept Ultrasonic sensors operating concept UT sensors utilize high speed ultrasonic signals to detect the presence of objects in the vicinity of the sensor. A drill pipe in front of an ultrasonic sensor reflects the ultrasonic signals back towards the transducer. The time delay between the excitation signal launched from the transducer and the reflected signal detected at the transducer is proportional to the round-trip distance between transducer and the object. 12
Figure 4 Ultrasonic measurement approach 13
Section 3 Risk analysis results A risk analysis was conducted on the various sensing techniques based on the evaluation criteria presented in section 1. A more detailed risk analysis is presented in the Sensor Integration Concept Rationale report. Summary of risk evaluation Power consumption: X-ray sensors require higher energy to power the high voltage x-ray generator source. High attenuation through the drilling mud requires a high x-ray photon flux to provide sufficient signal for detection. Electromagnetic sensors require approximately 2 watts of power, with the receive signal conditioning being less than 0.5 watts. The UT sensors are expected to consume 1 watt per sensor for the combined sensor excitation, and high speed data processing. Ultrasound sensors are expected to consume 1 watt per sensor for the combined sensor excitation, and high speed data processing. Since five UT sensors are expected to provide sufficient coverage circumferentially around the BOP annulus, the UT sensors are expected to consume approximately 5 watts of power. While 100% duty cycle for both EM and UT sensors result in power consumption that is compatible with the overall requirements, additional power savings can be attained by reducing the sensing duty cycle. If duty cycle control is utilized, each of the sensors would switch between a sleep mode and an active mode. During the sleep mode, the sensor is in a low power state. During the active mode, the sensor performs the sensing operation, and returns to sleep mode once the operation is completed. The low overall sensing bandwidth required (~5 Hz) coupled with fast detection rates for both EM and UT sensors (>100Hz) enable duty cycles of approximately 10% to be achievable. This reduction of duty cycle can provide power consumption improvements of 2-5x. Marinization capability: Compared to the other sensing modalities, X-ray sensors have the constraint of needing to marinize a high energy x-ray tube. While subsea x-ray has been used for inspection, long term survivability of x-ray tubes in subsea environments is unknown, and poses a reliability risk. Ultrasound sensors have been used in subsea applications for both inspection and flow measurements. A number of subsea capable sensors are available. Electromagnetic sensors are simple to marinize since the sensor primarily consists of wire windings that are inherently high pressure capable. Protective sleeves and plugs made from a high density peek material for both ultrasound and electromagnetic sensors will improve the life and aid in the marinization potential of the sensors without negatively affecting the measurement capability/ 14
Position sensitivity: All three sensor types suffer from error due to changes in drill pipe position. X-ray sensors work on the principal of creating a projection of the object in the path of x-rays. Due to x-ray divergence, and limits on the size of the detector, measurement uncertainty increases due to pipe position changes EM sensors are relatively insensitive to pipe position variation when the pipe moves slightly of center, but as the motion increases, a reduction in the output is observed. Ultrasound measurements work on the principal of detecting time of flight to determine distance. Since pipe position changes result in difference changes, uncertainty between position and diameter increases producing a diameter detection error. Pipe movement: X-ray: Photon detection rate of approximately 1 per second was observed. Since 10 s to 100 s of photons would be needed for reliable detection, integration time of 10 s to 100 s of seconds would be required. Since pipe motion is expected to be substantial over that time period, the x-ray measurement suffers from blurring of the detection signal due to motion artifacts. Electromagnetic and Ultrasonic measurement time of few milliseconds was achieved for both sensor type. These short integration periods are capable of performing the measurement in the presence of pipe motion. Sensor health: x-ray sensors: a detector area that is larger than the pipe diameter is required for the sensing to accurately detect the pipe diameter. Health checks between the area of the detector observing the pipe, and adjacent areas that are observing the background signal can be used to determine the health of the x-ray source and detector elements. EM sensor system consists of one excitation and 2 receive coils, signal consistency checks between the two receive coils individually as well as the combined differential output provides health information on EM system health. Minimum signal level, maximum harmonic distortion, and maximum mismatch between the two receive chains provide a means of detecting sensor failures. Circumferentially placed UT sensors ensure that for most pipe locations, at least 3 sensors are capable of detecting the presence of the pipe at any given time. At several locations, all 5 sensors are capable of detecting the pipe position. UT sensor health can be determined by identifying sensors with outputs inconsistent with the other sensors, and flagging the data appropriately. Capability of integration in BOP: The ferromagnetic steel typically used in BOP body construction causes substantial signal attenuation for both x-ray and EM sensors. Wetted sensors can reduce the effect of signal losses in the BOP body. The effects are eliminated altogether for the ultrasound sensors, and reduced substantially for the EM sensors. 15
Measurement in drilling mud: Both x-ray and ultrasonic measurements are attenuated in drilling mud. Attenuation of x-rays is such that only a few x-ray photons per second are detected in the presence of drilling mud. Ultrasonic signals suffer attenuation that is substantially higher than that in water. Lab characterization indicates that detection distances of 10 inches or higher is possible even in the presence of highly attenuating drilling mud. Analysis and modeling shows that with circumferentially spaced sensors, measurement ranges as low as 6 inches is sufficient to locate and determine the diameter of a drill pipe in the BOP annulus. Low frequency electromagnetic sensors are insensitive to the presence of drilling mud making the measurement robust to drill mud characteristics. Signal conditioning and processing requirements: All three sensor types require some high speed processing in order to perform the measurement. The details of the signal processing are presented in more detail in section 4 of this report. A summary of the results are presented in table 2. Criteria for evaluation X-ray Electromagnetic Ultrasound Power consumption Marinization capability Insensitivity to pipe position Insensitivity to pipe movement Ability of sensing system to determine the health of the sensor Capability of integration in BOP Measurement capability in drilling fluid Sensor signal conditioning and processing requirement Sensing system response time Sensor bandwidth Power consumption Compatibility with 19" cavity size OD measurement Range Resolution in detecting diameter change Resolution in diameter reading Communication data rate (on MUX cable) Temperature range of electronics 16
Electronics packaging Temperature range of sensor Placement in or close to BOP Table 2: Risk analysis results for the various sensing techniques Section 4: System configuration based on risk assessment Based on the risks and mitigations presented in section 2. The sensing system is envisioned to utilize both electromagnetic and ultrasonic sensors. A table summarizing the various EM sensor system risks and the ensuing mitigation approach is summarized below and presented as the justification for the sensor system configuration recommendation. Table 2: EM sensor risks and mitigation approach Risk EM losses in BOP body Signal sensitivity Signal dependence on pipe position Drilling fluid dependence Mechanical robustness Mitigation Wetted sensor reduces need for signals to travel through ferromagnetic steel Low excitation frequency suffers less loss Differential sensing enables higher gain and increased sensitivity 3-coil differential signal amplifies pipe diameter difference, reduces dependence on absolute measurements Low frequency excitation robust to characteristics of drilling fluid high density PEEK protective layer provides protection, doesn't adversely affect measurement Similarly, the UT sensors approach is summarized below: Table 3: UT sensor risks and mitigation approach Risk UT losses in BOP body sensor range Signal sensitivity Signal dependence on pipe position Drilling fluid dependence Mitigation Wetted sensors eliminate loss through BOP body multiple sensors circumferentially spaced to cover the pipe location in bore Time gain correction increases signal gain for more attenuated signals from lo multiple sensors circumferentially spaced are capable of detecting pipe position and diameter Low frequency excitation suffers from least attenuation in drilling mud. 9-12" of measurement range possible 17
Mechanical robustness high density PEEK protective layer provides protection, and acts as a mechanical impedance matching buffer between sensor and mud Sensor system configuration: A system consisting of multiple circumferentially placed UT sensors is needed to detect the diameter of the pipe. 5-UT sensors provide sufficient coverage to perform the detection in the presence of error sources such as pipe position uncertainty. 3-coil EM sensors in a single-transmit, differential-receive configuration is capable of performing the measurement in while eliminating errors due to pipe offset. While both EM and UT sensors in the described configurations are capable of performing the measurement independently, as described in risk tables 3, 4 and 5, the EM and UT sensors have different sensitivities to the error sources. This difference may be utilized to use one sensor type to correct for errors in the other. Phase 2 will finalize the prototype sensor system configuration and develop the signal processing algorithms to evaluate data correlation between the sensors. The test prototype will be used to evaluate the EM and UT sensor systems individually as well as the combination of the two. Based on the detailed design phase and the prototype test results a final configuration down selection of EM, UT or a combination of the two will be conducted. The overall mechanical integration concept is shown below. Figure 5: Overall system mechanical integration approach The pressure ports utilized for the EM sensor wires and the UT transducers are similar to those already utilized currently in BOP systems for the well bore temperature and pressure monitoring sensors. 18
For EM sensors, a local phase and amplitude signal process is needed to convert the parameters of the received sinusoid into the scalar low speed amplitude and phase angles. These numbers need only be updated at a rate of comparable to that of the response time needed from the sensing system. 1 to 10 updates per second is typical, and is sufficiently low to enable integration with existing BOP input channels. Figure 6: EM sensor receive chain block diagram The UT sensors require fast data collection 100+ K Samples per second to provide sufficient timing resolution. Signal processing algorithms for noise reduction and improved resolution (such as time gain correction and cross correlation) need to operate on high speed data. The output from the high speed signal processing is a low speed time of time of flight (and hence distance) measurement between the sensor and the pipe. That distance measurement is also expected to be updated at a similar rate of 1 to 10 updates per second which is sufficiently low to enable integration with existing BOP input channels. 19
Figure 7: UT sensor receive chain block diagram Summary and conclusions: Sensing system risks due to attenuation in drilling fluid, errors due to pipe motion and pipe position require a multi-sensor system that includes multiple circumferentially placed ultrasonic transducers, differential electromagnetic sensors, or a combination of the two. Local signal processing is needed to provide local signal conditioning and data reduction providing a reduction in signal speeds to be conveyed to the BOP electronics, control and communication system. Total sensing system power consumption of <10 watts expected, with additional 2-5x reduction possible with duty-cycle control. 20