Technological Advances in Water-less Fracking: A Case Study

Hydrofracking transfigured the concept of producing from unconventional reservoirs. The Fracking fluid used in fracturing has unlocked many tight reservoirs but in terms of an aquifer, it poses threats like consumption of large quantity of water and also, used water becomes polluted as well as recycling cost is uneconomic. This paper evaluates alternatives to water-based frac fluids and discusses their environmental & economic impact along with resource availability and commercial feasibility. Pure Propane Fracturing uses propane in combination with non-toxic man-made proppants (light glass & carbon fullerene microbeads) with desired properties. Pure Propane is fluorinated and carbonated without water or harmful additives, thereby eliminates the risk of catching fire. Pure Propane Fracturing eliminates the need for water completely and thus, a perfect option for fracturing in water scarcity regions. Fracture flow capacity of Pure Propane can be enhanced with the use of phase change chemical proppants in the slurry stage. CO2 Foam Fracturing predominantly comprises liquid carbon-dioxide which reduces the water requirement up to 80%. CO2 foam-based frac fluid uses relatively fewer chemical additives as compared to the water-based frac fluid which in-turn does minimal formation damage. Foam Fracturing fluids have high fluid recovery and clean-up efficiency. CO2 foam-based frac fluid is available in a wide range of viscosities and can also work in high pressure high temperature conditions at significantly low polymer loadings. Energized frac fluid comprises N2/CO2 (20-30%) which reduces water consumption and provides additional energy to aid in load recovery during the post-frac flow-back stage. N2 gas can propagate more easily into small pores and micro-fractures to get lower breakdown pressure and enhance fracture complexity & CO2 exists in dense phase at static bottom hole conditions, thus is less susceptible to dissipation and dissolves in crude oil which reduces its viscosity and improves cleanup and recovery.

Investigation of Proppant Distributions in Rock Fractures With Applications to Hydraulic Fracturing

Hydraulic fracturing or fracking is a procedure used extensively by oil and gas companies to extract natural gas or petroleum from unconventional sources. During this process, a pressurized liquid is injected into wellbores to generate fractures in rock formations to create more permeable pathways in low permeability rocks that hold the oil. To keep the rock fractures open after removing the high pressure, proppant, which typically are sands with different shapes and sizes, are injected simultaneously with the fracking fluid to spread them throughout rock fractures. The extraction productivity from shale reservoirs is significantly affected by the performance and quality of the proppant injection process. Since these processes occur under the ground and in the rock fractures, using experimental investigations to examine the process is challenging, if not impossible. Therefore, employing numerical tools for analyzing the process could provide significant insights leading to the fracking process improvement. Accordingly, in this investigation, a 4-way coupled Computational Fluid Dynamic and Discrete Element Method (CFD-DEM) code was used to simulate proppant transport into a numerically generated realistic rock fracture geometry. The simulations were carried out for a sufficiently long period to reach the fractures’ steady coverage by proppant. The proppant fracture coverage is a distinguishing factor that can be used to assess the proppant injection process quality. A series of simulations with different proppant sizes as well as various fracking fluid flow rates, were performed. The corresponding estimated fracture coverages for different cases were compared. The importance of proppant size as well as the fluid flow rate on the efficiency of the proppant injection process, were evaluated and discussed.

Experimental Investigation into the Effects of Fracturing Fluid-Shale Interaction on Pore Structure and Wettability

One of the main techniques for the exploitation of shale oil and gas is hydraulic fracturing, and the fracturing fluid (slick water) may interact with minerals during the fracturing process, which has a significant effect on the shale pore structure. In this study, the pore structure and fluid distribution of shale samples were analyzed by utilizing low-pressure liquid nitrogen adsorption (LP-N2GA) and nuclear magnetic resonance (NMR). The fractal analysis showed that the pore structure of the sample was strongly heterogeneous. It was also found that the effect of slick water on pore structure can be attributed to two phenomena: the swelling of clay minerals and the dissolution of carbonate minerals. The swelling and dissolution of minerals can exist at the same time, and the strength of them at different soaking times is different, leading to the changes in specific surface area and pore size. After the samples were soaked in the slick water for two days, the contact angle reached the minimum value (below 8°), which means the sample is strongly hydrophilic; then the contact angle increased to above 38° with longer soaking times. The connected pore space in the shale matrix is enlarged by the soaking processing. Therefore, an in-depth understanding of the interaction between the fracking fluid and shale is essential to deepen our understanding of changes in the pore structure in the reservoir and the long-term productivity of shale gas.

Fracking, worksite injuries, and Aeromonas infection

Hydraulic fracturing or fracking is a method of extracting natural gas from the earthusing high pressure drilling equipment and fracking fluid that contains proppant and variouschemicals. It poses health risks to workers at the drilling sites, has effects on water and airquality, and creates potential health risks for people living near the drilling sites. A 30-yearoldman with no past medical history presented as transfer from an outside hospital after anexplosion on a fracking job site. This explosion released over 6000 pounds of water that threwhim 20 feet across the rig. He had radial and ulnar fractures in his right arm and digital fractureson his right hand. He also had trauma to his left knee and right posterior thigh with a largefluctuant Morel-Lavallee lesion. On day 3 the patient developed hypotension, lethargy, andnew onset fever from a possible infection of a hematoma; he was started on norepinephrineand intubated due to a decreased mental status. Cultures from the thigh were positive forAeromonas species. Aeromonas is a Gram-negative rod that is found in many environmentsthat contain water. Studies have shown that this organism grows commonly in West Texas andNew Mexico in river beds and lakes. Healthcare providers should keep Aeromonas spp in theirdifferential list of pathogens in patients with abrasions and open injuries that occurred aroundor in a body of water.

Ionic Fracture Fluid Leak-Off

The study is motivated by monitoring the space orientation of a hydrolic fracture used in oil production. Streaming potential arises due to the leakage of ionic fracking fluid under the rock elastic forces which make the fracture disclosure disappear after pumping stops. The vector of electric field correlates with the fracture space orientation since the fluid leakage is directed normally to the fracture surfaces. We develop a mathematical model for the numerical evaluation of the streaming potential magnitude. To this end, we perform an asymptotic analysis taking advantage of scale separation between the fracture disclosure and its length. The contrast between the virgin rock fluid and the fluid invading from the fracture is proved to be crucial in a build up of a net charge at the invasion front. Calculations reveal that an increase of the viscosity and resistivity contrast parameters results in an increase of the streaming potential magnitude. Such a conclusion agrees with laboratory experiments.