COST-EFFECTIVE DEVELOPMENT OF LACUSTRINE SHALE OIL IN BOHAI BAY BASIN, CHINA: CONNECTIVITY, WETTABILITY, MOVABILITY, AND FRACABILITY (Invited Presentation)

Shale oil development from lacustrine depositions in China has been showing major breakthroughs towards economic and sustainable production, but also implicated with a steep production decline in stimulated shale formations. Working with Paleogene-aged Shahejie and Kongdian Formations with low to moderate maturity in Bohai Bay Basin, China, this presentation shows that the limited matrix-fracture interaction (e.g., anomalous matrix feeding of petroleum molecules from the poorly-connected matrix pore space to the hydraulically-stimulated fracture networks) is the root cause of steep initial decline and low overall recovery. The matrix-fracture interaction is influenced by connectivity, wettability, movability, and fracability of shale formations, such as a predominance of minerals-related and generally water-wet pore space in shales of low to moderate maturity. However, there is a poor pore connectivity of fine-grained shale matrix with a wide spectrum of nm-μm sized pore networks to lead to anomalous diffusion and limited movability, and it’s important to assess the fracability to generate intensive fracture networks to reduce the matrix feeding distance for a sustained shale petroleum production. This is achieved by utilizing a set of complementary and experimental approaches such as porosimetry (mercury intrusion porosimetry, low-pressure gas physisorption isotherm, nuclear magnetic resonance), imaging [X-ray computed tomography, Wood’s metal impregnation, field emission-scanning electron microscopy (SEM), focus ion beam-SEM, µm and nm-CT), scattering (ultra- and small-angle neutron and X-ray)], the utility of both hydrophilic and hydrophobic fluids and associated tracers as well as fluid invasion tests (imbibition, diffusion, vacuum saturation) followed by laser ablation-inductively coupled plasma-mass spectrometry imaging of different nm-sized tracers.