Wellbore Monitoring in Carbonate Reservoirs: Value of DTS in Acid Stimulation through Coiled Tubing

Abstract

In acid matrix stimulation, the correct placement of the injected fluids is essential. Several diversion and placement techniques are often applied to obtain the desired fluid placement (Glasbergen and Yeager 2010). Distributed temperature sensing (DTS) and coiled tubing (CT) pressure, temperature, and collar locator tools were used to monitor the fluid placement and effectiveness of the diversion process.Real-time monitoring was required as part of the overall reservoir management strategy for the Tecominoacán 705 well. The CT service provided ideal conveyance for DTS in this highly deviated and depleted well. In a distributed-temperature survey, the fiber optic served as the sensing element, and combined with CT conveyance and pressure/temperature/collar locator tools, enabled continuous wellbore temperature monitoring across the entire horizontal while pumping a stimulation treatment through an annular space consisting of acids and diverters. It also allowed real-time decision making based on the actual measured injection profiles.This well was highly deviated in a carbonate reservoir, completed with 675 m of 4 1/2-in., 12.7 lb/ft liner and swell packers, with 150 m of tubing conveyed perforating (TCP) perforations distributed in six intervals. The DTS combined with CT tools provided accurate monitoring of the stimulation treatment, which was pumped through the annulus between the production tubing and CT. With the DTS service, it was observed that the stimulation fluids were injected only at the heel of the well, which was acting as a thief zone as a result of the presence of highly conductive natural fractures. Several stages of diverters were pumped to attempt to divert acid from the heel to the tip of the well, without success. The decision to cancel the final acid stages saved USD thousands in fluid costs. Mixing the acid on-the-fly using special blending equipment allowed the optimization of resources based on real-time decisions influenced by the DTS injection analysis.

Wellbore Cool Down During Hydraulic Fracturing Simplifies Using Dissolvable Materials

“…Numerical modelling can be used to predict the temperature cool down. Coupled real-time stimulation temperature modelling shows that hydraulic fracturing will cool the casing to the fracture fluid temperature within a minute of the arrival of the fracture fluids at location [8]. The cooling is particularly rapid at the modelled 69bbl/min pump rate.…”

“…The cooling effect of circulating mud during drilling has been measured and numerically modelled [5] and has implications for borehole stability [6]. During acid stimulation, distributed fiber-optic measurements have demonstrated the cooling effect of the injected fluid [7] and have used this distributed measurement to determine where the acid is entering the formation [8,9]. Similarly, distributed fibre optics has been used to describe the cooling effects during hydraulic fracturing [10,11].…”

2 1/8-in. Intelligent Coiled Tubing System Improves Operational Efficiency

“…Among those, the most advanced ones employ a 1/8-in. insulated electrical conductor (Taggart et al 2010(Taggart et al , 2011Oberascher et al 2012;Livescu et al 2015) or an optical fiber (Aviles et al 2011;Garcia et al 2011;Ramondenc and Baez 2013;Ahmed et al 2014a,b;Gorgi et al 2014;Ramondenc et al 2014;Webb et al 2014;Medina et al 2015). The BHAs for both systems were designed to meet similar requirements.…”