Modeling of distributed temperature sensing (DTS) responses and impacts of the cable location in horizontal wells

Abstract

Distributed temperature sensing (DTS) is a valuable diagnostic method that provides insight into completion design efficiency and production performance of unconventional assets. The temperature profiles obtained from these surveys are used to qualitatively and quantitatively assess the multi-stage hydraulic fracture placement efficiency and determine subsequent production profiles in horizontal wells. This work presents a methodology to predict the adverse measurement effect caused by the radial separation of the DTS fiber cable from the casing's outer surface. The methodology was applied on a field data set and the radial separation profiles were predicted using the DTS data and the constructed near-wellbore thermal model. It was found that the field data observed temperature oscillations were corresponding to the radial separation of the cable from the casing. It was determined that the fiber cable can separate as much as 1.36 inches away from the casing which in turn can cause up to a 40 degF deviation from the true temperatures. The initial cooldown from the geothermal temperature was determined to be a critical source of data for quantifying the cable location effect and the cable location profile. Recommendations on acquiring and cataloging DTS data from this portion of the hydraulic fracturing operations are provided. Additionally, the effect of near-wellbore temperature transients on DTS channels were quantified. Using this quantification, a methodology was constructed to predict the near-wellbore temperature distributions using DTS measurements. Synthetic examples along with sensitivities to various parameters are provided. The time behavior of the radius of investigation of the DTS on the near-wellbore temperatures was also calculated and is presented.