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DRILLING LABORATORY THE WOODLANDS, TEXAS. EVALUATION OF TARIJA FORMATION SAMPLES. PRESENTATION HIGHLIGHTS. Simulator test objectives Inefficiencies relating to drilling the Tarija Formation Hughes Christensen drilling laboratory overview Pressure simulator overview
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DRILLING LABORATORYTHE WOODLANDS, TEXAS EVALUATION OF TARIJA FORMATION SAMPLES
PRESENTATION HIGHLIGHTS • Simulator test objectives • Inefficiencies relating to drilling the Tarija Formation • Hughes Christensen drilling laboratory overview • Pressure simulator overview • Tarija sample outcrops in Bolivia • Mineralogy test results of the Tarija formation • Pressure simulator test results on two samples • Results evaluation • Suggestions
PRESSURE SIMULATOR TEST OBJECTIVES • Cost reduction on rig test vs. lab test • Prove drilling behavior of diamectites with different cutting structures • Mechanical Specific Energy (MSE) while drilling • Final bottom imprint • Drilling dysfunctions related to rock type • Obtain knowledge to design new cutting structures • REPSOL-YPF co-sponsored the test and provided the samples
DRILLING BEHAVIOR ON THE FIELD • Low efficiency = Low ROP = High drilling cost • OC and TR as main wear pattern • Limited drilling hours (more bit trips) = High drilling cost • High MSE • Bit and BHA vibrations • Optimization target is unknown and also hard to reach
OFF-CENTER DRILLING • Rock-Bit interaction • Poor lateral bit stability (BHA and Bit design) • High RPM • Bottom pattern generates track between the rows of inserts • Low efficiency = Low ROP = Short bit runs = Severe wear on bits • Can be associated to natural BHA imbalance • Bit cutting structure also affects behavior
OFF-CENTER ROTATION • OC simulation of a bit cutting structure • Movement is actually very subtle • Generates bottom tracks of formation between the rows of inserts
OFF-CENTER SYMPTOMS • Wear pattern concentrates on the cone shell • Can lead to exposing cone bearing (loss of cone) After the run Off-Center New Bit
OFF-CENTER SYMPTOMS • More severe cases under unstable conditions • Shirttail wear on one cone normally reveals OC behavior After the run Off-Center = Loss of the nose New Bit
TRACKING • Tracking simulation of a cutting structure • Bit inserts don’t cover the entire surface • Inserts fall in the same cavity left by a previous insert • Can be coupled to OC mode in certain situations Tracking No Tracking
TRACKING SYMPTOMS • Marks in between the inserts • Inserts with self-sharpening shape • Normally occurs in the outer rows of inserts (more probability) Marks in between inserts
MSE = MECHANICAL SPECIFIC ENERGY • Can be used to quantify drilling efficiency • Hard to measure on the field (bottom hole parameters normally not available) • Requires measurements very close to the bit • Higher WOB = Higher MSE • Higher RPM = Higher MSE • Higher TQ = Higher MSE • Lower ROP = Higher MSE • Efficiency = 1 = MSE / UCS
PRESSURE SIMULATORThe Woodlands, Texas • Indoor drilling laboratory • Simulates drilling conditions up to 6700m • Can be used to test bits under virtually any bottom hole condition • Analysis of parameters • Sensors measure bit-rock interaction • Bottom hole imprint after test • Simulates hydrostatic conditions
TARIJA SAMPLES - BOLIVIA • Initial mineralogy test samples from Bermejo (Rock A) and Huacaya (Rock B) • Pressure simulator samples form Aguarague (high clay content) and Isiri (high quartz content)
TARIJA SAMPLES – MINERALOGY TEST • Smaller samples for mineralogy tests • Rock sample A from Bermejo area • Rock sample B from Huacaya area
MINERALOGY TEST RESULTS • Both rocks are basically the same type according to spider plot • The rock in both cases is medium strength under Mohr-failure envelope • Higher quartz content reflects higher UCS values • P-S wave behavior shows dissimilar strength behavior • Higher clay content (lower UCS) seems to act as a harder rock under confinement • Linear relation of UCS may not be a good value to look at when evaluating diamectites
SIMULATOR TEST SAMPLES • ISIRI samples show greater compaction and also greater sand content • AGUARGUE samples show higher clay content, very fractured and low strength. Weathering process show effect on all samples
SAMPLES AFTER CUTTING • 4 large samples from ISIRI are sent to Savannah, Georgia for cylindrical cutting process • Only 2 samples survive transport and cutting process (fractured rock) • Surviving samples are protected by fiberglass coating
PRESSURE SIMULATOR TESTS • Test both samples under equal conditions • SAMPLE A: 12¼” GX-09DX (IADC 437), 7 inner rows, 3 outer rows, 88 compacts • SAMPLE B: 12¼” EP6312 (IADC 517), 8 inner rows, 3 outer rows, 133 compacts • RPM: 150 • WOB: 15-20-25-30-35 Klbs • 450GPM, Water based mud 9.5ppg, Nozzles 3x15, TFA = 0.52in² • 1.47 HSI • 5800 PSI confinement pressure
TEST A: 12¼” GX-09DX • Bit with no damage • Formation-inserts sloughing on the bottom • OC initiation (ledges on the wall) • TR on bottom visible • Hard-Sandy formation with ductile behavior?
TEST B: 12¼” EP6312 Bit with no damage Cleaner bottom imprint No formation-insert sloughing Very minor tracking evidence No ledges on the wall
RESULTS AND COMPARISON • ISIRI samples show 95% quartz content • Previous samples ROCK A-B show 71% and 58% of quartz content respectively • Color and texture of the rock seem to differ from original samples • First sample was stuck for 5 days after the test due to fines generation (seals blocked) • UCS values of simulator samples are close to 26KSI which are closer to certain types of granite rock
PRELIMINARY CONCLUSIONS • EP6312 (new M features) is better adapted to formation properties • Need to validate results with a field run • Diamectite rock has quite unique properties (hard-ductile-wave resonance) • UCS is not a good index for diamectites • OC and TR are clearly related to cutting structure design • DART to implement features on 16-28” bits • More testing of samples is required to get a better idea on additional rock beahvior