Inversion of Distributed-Temperature-Sensing Logs To Measure Zonal Coverage During and After Wellbore Treatments With Coiled Tubing

Abstract

Distributed temperature sensing (DTS) is a fiber-optic technology that provides continuous temperature profiles along the length of a well. When placing the fiber inside a coiled tubing (CT), one can monitor the temperature evolution while pumping as well as during a shut-in period. This evolution, in turn, yields some indications about the fluid-placement performance or zonal coverage. So far, interpretation of such DTS traces has been mostly qualitative. The work presented here demonstrates how DTS data can be used, coupled with an inversion algorithm and a forward model of fluid injection into a reservoir, to quantify the intake profile of treatment fluid along the wellbore. Recent field cases of matrix acidizing treatments in carbonate reservoirs are analyzed to illustrate the workflow and how it may yield valuable information. from Universidad de los Andes, Colombia.Kaveh Yekta-Ganjeh, P. Eng., SPE, is a senior technical engineer in coiled-tubing services at Schlumberger in Calgary. He has 10 years of experience in oilfield industry, all in coiled-tubing services. Yekta-Ganjeh joined Schlumberger in 2001 and has held different positions in field operation and technical support. He has worked in Iran, UAE, Libya, and Canada in land and offshore operations. Yekta-Ganjeh holds a BS degree in mechanical engineering from Sharif University of Technology, Iran.

Using Fiber-Optic-Enabled Coiled Tubing to Quantify Fluid Placement and Optimize Stimulation Effectiveness During Matrix Stimulation Treatments in Carbonate Reservoirs

“…Aside from guiding the placement of fluid during the subsequent stages of the treatment, one of the benefits of the method is to evaluate the repartition of fluid intake along the wellbore, thus helping with proper management of stimulation fluid resources based on the real needs for the wellbore (e.g., some zones may require less diverting agent/acid than initially thought of during the design phase). As previously stated in earlier studies (Al-Najim et al 2012;Tardy et al 2012), the quantification approach shows some limitations when temperature evolution are limited or noisy, or when the fiber feature some erratic point measurements. The later can be mitigated by a thorough quality control of the acquisition system and its measurements, and by always complementing the inversion algorithm with a qualitative assessment of the DTS evolution, along with the bottom-hole point readings provided by the BHA of the FOECT.…”

“…When bullheading was not possible and FOECT was moved to place the preflush fluid, it must be returned to deepest possible depth before starting this DTS measurement. This acquisition should be no less than 3 hours with the well shut in in order to allow enough time for the thermal response to occur at the reservoir and wellbore levels (Tardy et al 2012). The longer the time, the more reliable the results of the future analysis.…”

“…The innovative concept described by Tardy et al (2012) consists in using the DTS survey data acquired during a shut-in period in conjunction with information about the reservoir (such as formation mineralogy, distribution of porosity, rock physical and thermal properties, reservoir fluid type) and about the injection stage immediately preceding the shut-in period (such as injection duration and injection fluid type). The inversion algorithm then evaluates a group of parameters that allow the best fit between temperatures simulated using the forward thermal model (Tardy et al 2011) and the DTS data monitored during shut-in.…”

“…The matching is achieved by adjusting key flow parameters of the fluid placement and carbonate acidizingspecific thermal models (e.g., Kalia and Glasbergen 2010;Tardy et al 2011) used for the simulation through an errorminimization (also called "inversion") algorithm. The end result is a zonal coverage plot corresponding to the injection stage directly preceding the shut-in DTS acquisition (Tan et al 2012;Tardy et al 2012). Although still fairly new, this interpretation avenue shows interesting potential and prospects, especially when used during the intervention, as shown by Al-Najim et al (2012) and Lopez et al (2013).…”

Advanced Understanding of Matrix Stimulation Treatments Through In-Job and Post-Job Evaluation of Real-Time Downhole Measurements with Coiled Tubing: A Case Study

“…In addition to the qualitative interpretation of the DTS acquisition during preflush, a quantitative study was performed using an inversion algorithm, which, coupled to a fluid placement simulator, allows determining the volume of fluid injected during an injection stage from the DTS data recorded during the subsequent warmback (Tardy et al 2011;Tardy et al 2012). The last track to the right of Fig.…”