Activation Rate of Seismicity for Hydraulic Fracture Wells in the Western Canada Sedimentary Basin

ABSTRACT The rate of M≥3 earthquakes associated with hydraulic fracturing (HF) in horizontal wells (HF wells) in the Western Canada Sedimentary Basin is estimated for the period from 2009 to 2019. The estimates are based on a statistical discrimination algorithm that uses an objective scoring function deduced from the observed spatiotemporal correlations between wells and earthquakes. A Monte Carlo simulation approach is used to test the efficacy of the scoring function in determining noncoincidental association rates, allowing for correction of the observed association rates for the expected number of false positives. The basin-wide average rate of association of M≥3 earthquakes with HF wells (2009–2019) is ∼0.8% on a per well basis. The susceptibility appears to vary by formation by more than an order of magnitude, ranging from ∼6% for HF wells in the Duvernay Formation to ∼0.07% for HF wells in the Cardium Formation. For some formations, there has been no observed association at the M≥3 level to date, but this does not necessarily imply that such formations are immune to induced seismicity.

Interwell connectivity analysis in a low-permeability formation using a modified Capacitance Model with application to the East Pembina Field, Cardium Formation, Alberta

From the 1950s to the present, the Cardium Formation has been extensively produced. Exploitation has moved from the high-permeability western areas to very heterogeneous lower permeability, “halo-oil” regions in the east. In this case study, we briefly summarize the geology and assess the degree of interwell communication in selected areas from the East Pembina Field. For the Interwell Connectivity (IWC) evaluation, we use a modified version of the Capacitance Model (CM-PW) for connectivity analysis in areal windows. The CM has been used to analyze flow rates to measure IWC. The direction of the largest IWC change agrees with the expected maximum stress direction in the Western Canada Sedimentary Basin. The model also captures differences between pre- and post-fracturing connectivities. The matches of predicted to measured production using the CM-PW are fair to good, 0.76 ≤ R2 ≤ 0.95.

A New Approach for Permeability Prediction With NMR Measurements in Tight Formations

Summary Prediction of extremely low permeability in tight reservoirs poses major challenges with traditional methods. Several studies have proposed nuclear magnetic resonance (NMR) permeability predictors, but these often give large errors when applied in tight formations. In this report, we describe a new method with NMR well-log measurements that decomposes the T2 spectrum into, at most, three Gaussian components. On the basis of parameters from the decomposition, we build a pore-size-based lithofacies model to predict whole-core horizontal permeability. With these parameters, we also modify the empirical Timur-Coates equation (TIM) to predict permeability. The NMR decomposition allows us to predict proportions of shale and silt. Applied to the tight Cardium formation, the parameters correlate strongly with core image and X-Ray-diffraction (XRD) results. In addition to Cardium data, we apply our approach to published data sets with good results, showing that the model gives accurate lithofacies-proportion estimates. To calibrate the model, Cardium probe permeameter data are used to identify facies permeabilities. Arithmetic-averaged permeability with the NMR-based model was calculated to compare with whole-core horizontal permeability. Monte Carlo analysis confirms the agreement between the model and core-permeability values. Our model provides a “bridge” to relate permeability between the probe scale (<1 cm laminations) and core size (>15 cm thin beds). Without the NMR well-log decomposition, Cardium TIM permeability predictions are in error by more than one order of magnitude in most intervals. The major challenge with the TIM model is obtaining an accurate T2 cutoff value. Compared with core-measured bound-water saturations, the default 33 ms value is too large for our tight samples. Our NMR decomposition, however, shows good correlation with measured bound-water saturations. With several core samples and NMR parameters, we modified the TIM model and found that it provides very good permeability predictions.