Feasibility Experiments for In-situ Reservoir Nano-Agents
Saudi Aramco, SA
Keywords: reservoir engineering, nanofluid, upstream E&P, nanoparticles, coreflood, pore network
Abstract:The advent of atomically accurate sensing and manipulation tools has spurred a widespread interest in nanotechnology with the prospect of reengineering matters and synthesizing functional systems from the ground up. This enabled thinking “outside-the-box” in valuable applications in biotechnology, medicine, material science, computing, energy, and most recently the upstream sector of exploration and production (E&P) in the oil and gas industry. The petroleum industry needs strong stable materials suited for use in harsh and corrosive environments. Nanotechnology could also provide new tiny metering solutions to address wellbore and reservoir sensing requirements in-situ. And smart fluids are being used to enhance oil recovery, limit water production with the oil, and reduce drag and friction forces during drilling. The capabilities become limitless with the dream of having functionalized nano-sized “agents” in the reservoir. To test the future reality of having molecular in-situ sensing and intervention means in the reservoir, we embarked on a research initiative to run core-flooding experiments on carbonate samples from the ARAB-D formations using inert nanoparticle suspensions. This was aimed also to set the stage for injecting traceable nanoparticles into the rock. Broadly, the study intended to generate baseline data for the injection response of nanoparticles in the carbonate bimodal samples and correlate the impact on the rock permeability and the particle transport efficiency in terms of particle size, concentration, and surface chemistry. Thirty coreflood tests were run on three groups of rock permeabilities. Supporting tests included micro-CT scanning, ESEM, EDX, and NMR T2 distributions. Cross-linked copolymer microsphere suspensions in ultra pure water were used as the injection nanofluid. These come in a variety of particle concentrations, sorting and sizes. The characterization of the effluent and influent suspensions of nanoparticles was done using a DLS device linked to an Asymmetric Flow Field Flow Fractionation (AF4) channel and controller and a chromatography digital fluorometer. This paper describes the procedures and results from these tests. A detailed characterization of the porous media structure combined with advanced imaging and modeling techniques has proved successful as a tool in the rapidly developing area of nanomaterials applications to E&P. Initial models for the transport and retention of nanoparticles have relied on a combination of models used for petroleum reservoir characterization (effective medium and pore network models), computation fluid dynamics (CFD) in pore scale micro-models and classical colloid filtration theory (CFT). Our modeled approach captured the fundamental observations of these tests in relation to particle retention and velocity but did so through the use of adjustable bulk parameters. In addition, a general testing program to identify the different mechanisms governing the mobility of the nanoparticles within the different pore network systems is proposed. The program is detailed and the general prospects of in-situ sensing and intervention for oil reservoir application are also outlined.