Abstract

Middle Cambrian sediments in the southern Georgina Basin contain multiple organic-rich source rocks and have been suggested to be prospective for both conventional and unconventional hydrocarbons. We present new geomechanical data collected from the middle Cambrian Arthur Creek Formation and Thorntonia Limestone in four wells (Baldwin 1, MacIntyre 1, Owen 2, Todd 1) in the southern Georgia Basin, and compare the data to mineralogical and geochemical datasets. Geomechanical test intervals were selected to allow geomechanical test results to be directly compared with the mineralogical and geochemical datasets (X-Ray Diffraction, HyLogger and organic geochemistry). Approximately 25 m of core was tested for unconfined compressive strength (UCS) using the scratch-testing technique, and results indicate values in the range of 60–150 MPa. Triaxial testing was also conducted to measure the poroelastic properties of core, and results indicated that Young’s modulus is generally in the range of 45–67 GPa. UCS and Young’s modulus are positively correlated and increase with depth through the prospective Arthur Creek Formation. The mechanical properties of the tested core are relatively indurated and stiff compared with young sedimentary rocks and broadly similar to proven shale gas plays in Australia and internationally. Mineralogically, the Georgina Basin rocks tested have lower clay contents than rocks from other Australian and international basins but no clear correlation was observed between geomechanical properties and mineralogy, suggesting that multiple factors contribute to the poroelastic and strength parameters. For example, parameters such as sonic velocity and porosity are weakly correlated to rock strength. Geomechanical data can be used alongside other datasets (e.g. sedimentological, geophysical and structural data) to better inform predictions of hydrocarbon prospectivity.

1. KEY POINTS

2. Middle Cambrian rocks from the Georgina Basin, Australia are prospective for conventional and unconventional hydrocarbons.

3. Rock mechanical tests are conducted to determine how the organic-rich sediments might respond to stimulation.

4. Mechanical analyses are evaluated alongside mineralogical, geochemical and well-log data to assess controls on rock strength properties.

5. Geomechanical behaviour is complex and appears to be driven by multiple factors.

摘要

乔治娜盆地南部的中寒武世沉积物中含有多种富含有机物的烃源岩，并被认为对常规和非常规烃都有潜在的前景。我们提供了从佐治亚盆地南部的四口井（鲍德温1，麦金太尔1，欧文2，托德1）中的寒武纪中段亚瑟河溪组和索通石灰岩采集的新地球力学数据，并将这些数据与矿物学和地球化学数据集进行了比较。选择地质力学测试间隔，以便将地质力学测试结果直接与矿物和地球化学数据集（X射线衍射，HyLogger和有机地球化学）进行比较。使用划痕测试技术测试了大约25 m的岩心的无侧限抗压强度（UCS），结果表明该值在60–150 MPa的范围内。还进行了三轴测试以测量岩心的孔隙弹性特性，结果表明，杨氏模量通常在45-67 GPa的范围内。UCS和杨氏模量呈正相关，并随着潜在的亚瑟克里克组的增加而增加。与年轻的沉积岩相比，被测岩心的机械性能相对坚硬且坚硬，与澳大利亚和国际上已证实的页岩气矿床大致相似。矿物学上，被测试的乔治娜盆地岩石的黏土含量低于澳大利亚和其他国际盆地的岩石，但在地质力学性质和矿物学之间没有观察到明显的相关性，表明多因素影响了孔隙弹性和强度参数。例如，诸如声速和孔隙度之类的参数与岩石强度之间的关系很弱。可以将地质力学数据与其他数据集（例如，沉积学，地球物理和结构数据）一起使用，以更好地为油气远景预测提供依据。

1. 关键点

2. 来自澳大利亚Georgina盆地的中寒武纪岩石具有常规和非常规碳氢化合物的前景。

3. 进行岩石力学测试，以确定富含有机物的沉积物对刺激的反应。

4. 力学分析与矿物学，地球化学和测井数据一起进行评估，以评估对岩石强度特性的控制。

5. 地质力学行为是复杂的，并且似乎受多种因素驱动。