Abstract The Jiamuhe formation in the Zhongguai uplift in Junggar basin is a formation with bulk of volcanics or volcaniclastics. This formation has been proved to be a good reservoir, despite the free water presence. From a petrophysical point of view, it has been a headache to clearly identify the fluids in the pores for the volcanic formation. In order to maximize the effectiveness of exploration, fluid identification is crucial to locate for the sweet spot to escape the water zone and secure the high productivity. This paper presents how a combined advanced well logging solution combining static and dynamic techniques revealing the fluids type in the volcanic formation. The workflow is based on wireline logging techniques, including advanced spectroscopy, borehole micro-resistivity images, T1- T2 based 2D nuclear magnetic resonance (NMR), array dielectrics and deep transient formation tester. Spectroscopy together with borehole image were used to identify the lithology and quantify the complex minerals, 2D NMR and array dielectrics were used to identify fluids in the static environment. Water-filled porosity can be inverted from array dielectric constant, while T1 and T2 distribution measured by a 2D high-resolution nuclear magnetic logging tool can be classified into potential different signal sources with advanced blind source cluster analysis method. Subsequently, combining the results from dielectric constant and 2D NMR, we finetuned the interpretation models, and the fluid properties corresponding to different fluids can be identified and summed, such as movable oil, bound water and movable water, etc. Finally, the sweet-spot interval can be identified with the driving factors. Deep transient formation testers acquired the fluid samples, performed the fluid analysis downhole, and mastered reservoir productivity and profiles dynamically. From the difference of the physical properties together with the hydrogen saturation, the sweet spot was recognized by finding out the interval with highest movable hydrogen porosity and lowest bound component directly. The recognition of irreducible components is crucial for escaping the water zone as the hydraulic fracturing was required for further development. The result provided key guidance for test layer selection and horizontal well landing. Deep transient formation testers verified the fluid properties and provided answers for the reservoir productivity. The entire workflow provided a novel approach starting from formation evaluation to the final production confirmation. All operations mentioned above lasted around 12 days, which provided a proven alternative solution to drill stem testing (DST) by accurately determining minimum hydrocarbon in place and zonal deliverability. The operation increases operational agility and eliminates airing and reduces carbon emissions in an effective way.
Renzhong et al. (2025) studied this question.