A multi-parameter fracture inversion method based on thermal neutron detection technology

• Published in: Journal of petroleum science & engineering 2020-05, Vol.188, p.106874, Article 106874
• Main Authors: Chen, Qian, Zhang, Feng, Liu, Yingming, Zhang, Quanying, Tian, Lili, Xie, Guanbao
• Format: Article
• Language: English
• Subjects: Fracture inversion; Monte Carlo; Thermal neutron detection
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2019.106874

Hydraulic fracturing plays an important role in enhancing oil and gas production of unconventional formations. The quantitative fracture evaluation is essential for the optimization of fracturing model and production prediction of oil or gas. In this paper, based on the high thermal-neutron absorption capacity of tagged proppants containing gadolinium oxide, the thermal neutron detection technology is proposed to determine the fracture parameters including the height and width. By Monte Carlo simulation method, the spatial distributions of the thermal neutron before and after fracturing are analyzed. The relationships of the thermal neutron count versus gadolinium content and proppant filling are studied. On this basis, a mathematical relationship between the change of thermal neutron count VTn and fracture parameters was established to quantitatively evaluate the fracture height and width. In addition, the fracture responses of VTn under different formation backgrounds including porosity, salinity and lithology width were studied. Results show that the variations of porosity, salinity and lithology have non-ignorable influence on the determination of fracture width. Therefore, the better method on the fracture-width inversion is combining the thermal neutron count with the formation parameters. A simulated fracturing case with different formation porosities, lithologies and fracture conditions is given, which presented the feasibility of the method under different measurement environments. After the corrections of porosity, salinity, and other formation backgrounds, the new method shows a good performance: the calculated results of the fracture width and height are consistent with the realistic parameters, and the error in fracture calculation is less than 10%. •A quantitative fracture inversion method based on thermal neutron detection technology was established.•The calculation method of fracture width was established.•The fracture responses under different formation backgrounds were analyzed.