Fracturing and permeability enhancement with laser technology employing fuzzy logic

Abstract

Increasing the rock permeability in low permeable zones of the hydrocarbon reservoirs by conventional methods will often cause formation damage and consequently will reduce the efficiency of recovery of the reservoirs in long term. The use of high energy laser technology as an alternative and innovative approach to mobilise heavy oil and improve permeability, as opposed to the conventional techniques, which have advert effects on the longterm reservoir productivity, was examined in this research. This paper will present study results of the employment of pulsed (Q-switched) Nd: YAG (Neodymium: Yttrium Aluminium Garnet) laser on impermeable heavy oil-bearing core samples which have been simulated in lab to be as close as possible to the real reservoir conditions.A unique technique was employed in this study where lasing experiment was conducted on samples followed by intervals of stopping lasing operation, known as relaxation intervals. The alternate lasing-relaxation intervals which were repeated for samples 3 times, yield positive and satisfactory results both for heavy oil mobilization as well as permeability improvement. Porosity increase was also observed due to fracture production. Specifications of applied laser pulses and their associated beam properties, samples characteristics and dimensions as well as the simulated experiment environment with that of the real reservoir conditions will be reported. Fuzzy logic was employed to normalize the varying and diverse parameters affecting the rock's thermal behaviour such as mineral content, fluid content and type and pressure.By employing the proposed technique on samples from heavy-oil-bearing low permeable zones of Burgan and Mauddud reservoirs of the Giant Burgan field in Kuwait, fractures were produced and permeability of the reservoir samples were improved to almost 3 times of their initial values in some of the samples. Upon the termination of the third lasing experiment, traces of oil could be observed on some of the core sample's surfaces, proving that the heavy oil was mobilised due to induced high temperatures generated in the samples during lasing.