Hydraulic Fracturing Down Under

McGowen, J.M.; Gilbert, John R.; Samari, Elham

doi:10.2523/106051-ms

Cited by 3 publications

(1 citation statement)

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“…The contact angle between the mercury and the siltstone used to calculate the pore size was 130°. Figure 2 shows the incremental intrusion volume vs. pore size in the mercury intrusion test, and the larger pore size at the first peak was caused by the destruction during the sample preparation process and the pore diameter ranges from several nanometers to several micrometers [24], which is Figure 2 shows the incremental intrusion volume vs. pore size in the mercury intrusion test, and the larger pore size at the first peak was caused by the destruction during the sample preparation process and the pore diameter ranges from several nanometers to several micrometers [24], which is confirmed by the SEM images in Figure 3. Although the siltstone was fine-grained, a high porosity up to 19.45% was obtained from the mercury intrusion tests.…”

Section: Sample Description and Preparationmentioning

confidence: 99%

Influence of Water Saturation on the Mechanical Behaviour of Low-Permeability Reservoir Rocks

et al. 2017

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Abstract:The influence of water on the mechanical properties of rocks has been observed by many researchers in rock engineering and laboratory tests, especially for sedimentary rocks. In order to investigate the effect of water saturation on the mechanical properties of low-permeability rocks, uniaxial compression tests were conducted on siltstone with different water contents. The effects of water on the strength, elastic moduli, crack initiation and damage thresholds were observed for different water saturation levels. It was found that 10% water saturation level caused more than half of the reductions in mechanical properties. A new approach is proposed to analyze the stress-strain relations at different stages of compression by dividing the axial and lateral stress-strain curves into five equal stress zones, where stress zones 1-5 refer to 0%-20%, 20%-40%, 40%-60%, 60%-80% and 80%-100% of the peak stress, respectively. Stress zone 2 represents the elastic range better than stress zone 3 which is at half of the peak stress. The normalized crack initiation and crack damage stress thresholds obtained from the stress-strain curves and acoustic emission activities averaged 31.5% and 83% of the peak strength respectively. Pore pressure is inferred to take part in the deformation of low-permeability siltstone samples, especially at full saturation levels. A change of failure pattern from multi-fracturing to single shear failure with the increase of water saturation level was also observed.

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Section: Sample Description and Preparationmentioning

confidence: 99%

Influence of Water Saturation on the Mechanical Behaviour of Low-Permeability Reservoir Rocks

et al. 2017

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Taking the First Steps: Stimulating the Nappamerri Trough Resource Play

Pitkin¹,

Wadham²,

McGowen

et al. 2012

SPE Asia Pacific Oil and Gas Conference and Exhibition

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The Nappamerri Trough in the Cooper Basin has long been recognised as a potential unconventional resource play with both deep-basin (Hillis et al. 2001) or basin-centred gas, and, more recently, as a potential shale gas target. However, initial attempts to fracture stimulate sandstones on conventional structural highs in and around the trough proved difficult. High treating pressures reached the limits of the well designs, and unsuccessful stimulation treatments resulted. A review of geomechanical information suggested that fracture complexity might have resulted from fractures initiating vertically and then twisting off to horizontal further into the reservoir (Nelson et al. 2007). From 2010 to 2012, Beach Energy undertook a two-well exploration drilling program aimed at assessing the shale gas potential of the Nappamerri Trough and proving the presence of gas outside of structural closure. The wells were initially planned to gather base geological information from the core, but it was recognised that key fracture stimulation uncertainties could be addressed by these wells that would have significant benefit for future well design. With the knowledge gained from previous stimulation treatments, the wells were designed to incorporate Acid-soluble cement to improve the connection to the reservoir A fracture completion string—wellhead and pumping equipment suitable for higher treating pressures A surface tiltmeter monitoring array to ascertain whether treatments were twisting into the horizontal plane The two wells, Holdfast-1 and Encounter-1, were successfully stimulated with 13 different treatments. This paper summarises the interpretation of the treating pressure data and the tiltmeter responses. Through diligent pre-project planning, the observed treating pressures were manageable, although higher than pressure gradients in other published shales and tight-gas areas. Large near-wellbore (NWB) pressure losses in most intervals were successfully reduced to allow treatments to be placed using moderately low viscosity fluids. The interpretation of the tiltmeter array data indicated predominately vertical fracture development, which is a positive outcome for maximising stimulated reservoir volume (SRV) in future horizontal wells. However, the fracture orientation determined from the tiltmeters was not consistent with the anticipated maximum stress orientation from borehole logs and regional studies, and further investigation is required to resolve this difference.

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Fracture Height Growth Study: Cooper Basin Probability Analysis

Griffiths

2018

SPE Asia Pacific Oil and Gas Conference and Exhibition

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A probability graph was developed to describe height growth potential when performing hydraulic fracture stimulation operations in the Cooper Basin, Central Australia. This graph has led to improvements in setting completion strategies. Multiple data sources were used to define the probability graph, including proppant tracers, microseismic, downhole tiltmeter data as well as pressure interference and production data. Each dataset has known uncertainties, so the empirically derived probability graph has an intrinsic range of uncertainty. The observed data shows instances of fracture propagation across changes in lithology which were previously thought to be highly confining. In other instances, field data closely matched model predictions. Likewise, the observed data indicates that typical levers used to induce or reduce height growth (such as fluid viscosity, pump rate and job size) may have limited influence. These insights led decision makers to question the validity of deterministic fracture models. This study highlights that fracture height growth predictions should carry a range of uncertainty. An appreciation of this range has proven beneficial by fostering ‘what-if’ discussions during the project planning phase. The derived probability graph can be used to run sensitivity analyses to determine the optimal path when several completion methods are available. This graph has proven to be an informative and practical tool for use in the Cooper Basin by promoting deeper thought and collaboration amongst stakeholders. Similar tools could be developed to characterise fracture height growth within other petroleum basins.

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Hydraulic Fracturing Down Under

Cited by 3 publications

References 0 publications

Influence of Water Saturation on the Mechanical Behaviour of Low-Permeability Reservoir Rocks

Influence of Water Saturation on the Mechanical Behaviour of Low-Permeability Reservoir Rocks

Taking the First Steps: Stimulating the Nappamerri Trough Resource Play

Fracture Height Growth Study: Cooper Basin Probability Analysis

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