12 th Annual Sucker Rod Pumping Workshop Renaissance Hotel Oklahoma City, Oklahoma September 27 30, 2016 Downhole Dynamometer Card Validation Method Omar Al Assad, Justin Barton, Kalpesh Singal, Shyam Sivaramakrishnan General Electric
Motivation Accuracy of pump card estimation is critical for rod pump control and downhole pump diagnostics Using two different approaches to estimate the pump card offers redundancy that can be used to associate a confidence level to the obtained pump card Pump cards with low confidence level may be used to trigger alarms for operator to check abnormal system behavior such as: 1. Noise in load cell measurement 2. Sticking pump 3. Acute pump speed change 4. Sudden pump fillage drop (intake obstruction) (Patent Pend 2016 Sucker Rod Pumping Workshop 2
Downhole Dynamometer Card Validation FS pump card 1 /stroke FD pump card Quasi real-time Norm Distance Pump card Confidence level Pump card validation can be done in real time on well controller to detect any malfunction or abnormal operation leading to different pump card calculation results It can be also considered for offline analysis 2016 Sucker Rod Pumping Workshop 3
Down Hole Dynamometer Cards 2 u t = 2 u u 2 a2 c x2 t Acoustic velocity a 2 = 144g ce ρ Damping c = 144c g c ρa Well depth up to 16000 feet 2016 Sucker Rod Pumping Workshop 4
Sam Gibbs Method - Fourier Series Surface Data Fourier coefficients n=1 Wave equation Analytical solution using Separation of Variable method for taper n n=n+1 Input T n =output T n-1 Last taper? no Inv. FS Transform yes Downhole Data Fourier coefficients Time Domain Frequency Domain 2016 Sucker Rod Pumping Workshop 5
Everitt-Jennings Method Finite Difference Discretized rod dynamics model: a 2 1 Δx + u i+1,j u i,j Δx = u i,j+1 2u i,j + u i,j 1 Δt 2 c u i,j+1 u i,j 1 2Δt 1 Δx u i,j u i 1,j Δx Equation recursively solved numerically across all tapers for u i+1,j with surface position and force measurements as inputs. Surface Model Inputs u 0,j = u pr,meas,j u 1,j = Δx EA F pr,meas,j + u 0,j N_ELEMENTS_TOTAL Model Outputs Pump u pump,j and F pump,j 2016 Sucker Rod Pumping Workshop 6
Case Studies Test condition Lufkin C912-365-168 Stroke 168 Pump 2 @ 4,401 Ft Motor Nema B, 60 HP Tubing Anchor 4,052 Diameter Number Installed Total Length Type/Grade 1.500 1 26 Polished Rod 1.000 60 1500 D Sucker Rods 0.875 60 1500 D Sucker Rods 0.750 47 1175 D Sucker Rods 1.625 8 200 Sinker Bars Total Depth 4401 Solver configuration Fourier Series Finite Difference Case Study : 1. Noise in load cell measurement 2. Sticking pump 3. Acute pump speed change 4. Sudden pump fillage drop (intake obstruction) Load Fourier coefficients =14 Position Fourier coefficient = 6 Sampling rate: 200 data pt/stroke Element size x=60 Sampling time t= 20 ms
Noise in load cell measurement Base line 1% noise on load measurement 2% noise on load measurement 2016 Sucker Rod Pumping Workshop 8
Sticking pump Sticking pump for few strokes due to a build-up 1 2 1 2 3 4 3 4 2016 Sucker Rod Pumping Workshop 9
Acute pump speed change 2 3 Pump Speed up : 2 SPM to 10 SPM 1 1 2 3 2016 Sucker Rod Pumping Workshop 10
Acute pump speed change 1 Pump Slow Down 8 SPM to 2 SPM Limited impact on Pump card 2 3 1 2 3 2016 Sucker Rod Pumping Workshop 11
Sudden pump fillage drop (intake obstruction) N-1 Pump fillage drop from 98% to 30% N N+1 2016 Sucker Rod Pumping Workshop 12
Conclusions and Perspectives The ability to calculate pump card using different methods on well controller offers opportunity for redundancy to associate a confidence level to the pump card Trigger pump card pattern matching This validation approach can be considered for real-time and offline analysis Deployment of this method on well controller will be considered for future studies on different well sites to analyze the impact of malfunctions on pump card estimation 2016 Sucker Rod Pumping Workshop 13
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