Advanced Petrophysical Surveillance Improves the Understanding of Well Behavior in Unconventional Reservoirs

Abstract

Abstract Multi-stage hydraulic fracturing in horizontal wells is an essential stimulation technique to enhance production and economics in unconventional tight gas sands in North America. However, one of the challenges that still remains is to understand and quantify the efficiency of each perforation cluster in order to optimize completions. Operators have used various production logging technologies in an attempt to understand completion efficiency. Even then, these low rate horizontal wells with unstable flow conditions and fluid segregation provide a challenging environment for production logging, and even the use of different tools / software provides no definitive answer. Absence of direct comparison between logging tools renders it difficult to assess the suitability of a particular tool in a given downhole environment. A field trial was thus conducted to acquire and compare the log data using two very different instruments, an array based logging tool and a downhole distributed fiber optic (DFO) with distributed temperature and acoustic sensing (DTS / DAS) capability. A multiple array tool, consisting of multiple spinner and resistance arrays, was deployed downhole via tractor into a well that had been on production for approximately three months. Multiple up/down passes were made at different speeds in both lateral and vertical sections to assist with spinner calibration. Following this, a retrievable DFO system (with both DTS/DAS) was run in the same wellbore and data was collected continuously for two days. A memory temperature tool was also added to the DFO toolstring to ensure post-acquisition temperature calibration and depth correction. This paper highlights the advantages and disadvantages of both logging techniques and suggests ways to improve flow profiling in low rate horizontal wells. It also shows that overall comparison of the data from the two tools looks good, with some differences resulting from the different nature of these measurements. This paper further shows how other surveillance data including radioactive proppant and chemical tracers, open-hole logs, cement bond logs, and geomechanical data in these horizontal wells can be used to complement the production logging results and provide insights to optimize future completions.