For more than 40 years, the industry has used pulsed neutron logging to determine hydrocarbon and water saturations behind casing for reservoir management. Multiphase saturation measurements over time are useful for tracking reservoir depletion, planning workover and enhanced recovery strategies, and diagnosing production problems such as water influx and injection fluid breakthrough. Cased hole logs also serve as a contingency when openhole logs cannot be run or are not considered for reservoir characterization.

Although the cased hole measurement suite has been greatly improved over many tool generations, the intrinsic physical measurements remained unchanged, which meant that operators could not obtain a complete picture of the rock and fluids behind casing. Input from openhole logs was required from a porosity or bulk density measurement for combination with the neutron porosity. Absent this input, primary formation evaluation in cased wellbores can be ambiguous. An additional challenge with cased hole logging is correctly compensating for the effects of borehole fluids and the presence of completion hardware.

An article in the Journal of Petroleum Technology “Tool Enables Complete Cased Hole Formation Evaluation, Reservoir Saturation Modeling” highlights a new tool developed to meet the need for accurate surveillance in cased holes. Pulsar multifunction spectroscopy service builds on innovative technologies to provide the first complete cased hole formation evaluation and reservoir saturation monitoring capability with openhole-equivalent measurements. The article includes a case study from North America. Read the full article here.

Learn more about other innovative technologies in the Schlumberger library of industry articles.