Water Distribution in the Montney Tight Gas Play of the Western Canadian Sedimentary Basin: Significance for Resource Evaluation

Abstract

Water distribution in unconventional gas reservoirs is a key parameter that influences many aspects of resource exploitation including selecting geographic areas for multi-well development programs, identifying target zones for horizontal wells, calculating reserves, estimating permeability, and understanding variability in gas and water production. Insights on water distribution in the Montney tight gas play of northeast British Columbia and northwest Alberta were gained by integrating reliable bulk volume water measurements from full-diameter core samples with other core, well log and geologic data. Water distribution in the studied Montney section was found to be related to stratigraphic architecture and rock fabric (defined by degree of bioturbation), and is interpreted to have been influenced by displacement efficiency of mobile formation water updip through tight Montney siltstones during hydrocarbon charging. Low gradient clinoform units with few shaly zones in the Lower Montney section enabled efficient water displacement and led to water contents close to irreducible water saturation. Higher gradient clinoform units with common shaly zones in the Upper Montney allowed less efficient water displacement, and significant volumes of mobile water were retained in parts of the section. Water saturation varies widely and directly influences effective gas permeability. A simple method for determining effective gas permeability from well logs was developed based on empirical relationships derived from the core and log data set. Effective gas permeability logs generated by this method help with the identification of target zones with superior reservoir quality for exploitation using horizontal multi-frac technology. A Pickett plot with effective gas permeability lines was found to be a useful tool for logbased comparison of Montney rock quality by stratigraphic zone or geographic area. This work shows that understanding water distribution and its influence on effective gas permeability leads to improved delineation of "sweet spots" for resource development in unconventional gas plays.

Nanopore-Structure Analysis and Permeability Predictions for a Tight Gas Siltstone Reservoir by Use of Low-Pressure Adsorption and Mercury-Intrusion Techniques

“…A larger data set of permeability measurements (pressure-and pulse-decay) on the same formation collected from multiple wells was provided by Wood (2012) and is reproduced in Fig. 19.…”

Study on the Distribution Characteristics of Formation Water in Tight Sandstone Gas Reservoirs of the Shan 23 Member in the Zizhou Gas Field of Ordos Basin

“…The logging characteristics of the formation water residue in the gas reservoir are as that of the gas layer in the well logging curves, and there is no obvious water layer information. This water type is relatively common in lithologic gas reservoirs but rare in structural gas reservoirs (Wood, 2012). The logging response characteristics are low natural gamma, high resistivity and low water saturation, which are comprehensively judged as a gas layer by log interpretation.…”

Impact of Solvent-Extraction on Fluid Storage and Transport Properties of Montney Formation

“…The precipitation of salt in the rock samples is dependent on the Љin-situЉ water/brine content and the salinity of the Љin-situЉ (formation) water. Wood (2013) reported that while water saturations (bulk volume water) in Lower Montney are generally less than 1%, the water saturations in Upper Montney commonly rang between 1 and 3%. Wood (2013) further reported that, while there is no significant interrelationship between water saturation and porosity in Lower Montney, the water saturation in Upper Montney increases with increasing porosity.…”

“…Wood (2013) reported that while water saturations (bulk volume water) in Lower Montney are generally less than 1%, the water saturations in Upper Montney commonly rang between 1 and 3%. Wood (2013) further reported that, while there is no significant interrelationship between water saturation and porosity in Lower Montney, the water saturation in Upper Montney increases with increasing porosity. As highlighted by Wood (2013Wood ( , 2015, these data indicate that, compared to the Upper Montney, the Lower Montney is most likely at irreducible water saturation.…”

“…Water-based hydraulic fracturing fluids generally have lower salinity than formation water, and therefore, the salinity of the produced water typically increases with time. This is particularly the case for the Montney due to the presence of hypersaline formation water which occurs as free or clay-bound water (Wood, 2013(Wood, , 2015. Due to the presence of hypersaline formation water, significant salt precipitation may occur after core retrieval from subsurface, affecting porosity and permeability.…”