During the past several years (i.e., 2006 to 2014), the US transformed the development of shale oil and gas from slow and steady into a shale gas boom by combining two already existing technologies—multistage hydraulic fracturing and horizontal wells. This helped the US once again be energy-independent regarding natural gas supply (Charlez 2015). Inspired by such success, the Kingdom of Saudi Arabia and the Middle East region are meeting the increasing energy demand by following similar steps (Bartko et al. 2012). Large stage sizes in hydraulic fracturing and horizontal drilling long laterals require large quantities of freshwater. Despite the fact that the Arabian Peninsula lacks freshwater resources, fresh water is still consumed by the oil and gas industry in the region. Conversely, seawater is plentiful and should substitute for freshwater in unconventional resource operations. However, the high salinity of seawater raises many chemical challenges in developing design criteria for fracturing fluids. To help mediate this problem, this paper studies the chemistry of developing seawater-based fracturing fluids using two types of polymers as gelling agents and compares results to already existing freshwater-based fracturing fluid data under different conditions. Various seawaters from around the world were compared to Arabian Gulf seawater and its various compositions throughout the year. The local seawater's high total dissolved solids (TDS) measurement is 54 000 mg/L and includes sulfate (>4000 mg/L), calcium (>600 mg/L), and magnesium (>1700 mg/L). These are the major ions that cause delayed hydration, alteration of the crosslinking mechanism, and high scale formation, along with barite (BaSO4). Moreover, the paper presents a better understanding of fluid behavior by studying the effects of sulfate (>4000 mg/L), calcium (>600 mg/L), and magnesium (>1700 mg/L) individually to observe fluid stability at high temperatures in both polymers.
As part of the continuous efforts to save freshwater resources in the Middle East, seawater-based fracturing fluid offers a high-potential solution to help save millions of gallons of fresh water while developing fracturing fluids for hydraulic fracturing applications. Scale deposition is one of the major technical challenges for fracture stimulations using seawater-based fluid. To understand the scale deposition and mitigation for fracturing using seawater-based fluid, a series of dynamic and static performance, compatibility, and thermal stability tests were conducted. Results showed that harsh scale forms with mixing raw seawater and high total dissolved solids (TDS) tested formation water at higher temperatures under dynamic and static conditions. Scale inhibitors cannot effectively inhibit scale deposition in such harsh scaling conditions because of the issues of compatibility and performance at static conditions. Nanofiltration of seawater is introduced to remove most of the sulfate ions in seawater and help significantly reduce the scaling tendency when mixing with high TDS formation water during fracturing treatments using seawater-based fluid. Combining the nanofiltration technique and scale inhibitor application, the scale issue during fracturing using seawater-based fluid can be effectively mitigated and was determined to be suitable for field application. The scale inhibitor showed good compatibility with nanofiltered seawater. The dynamic scaling tests were successful when the proper scale inhibitor and optimum concentration were used, while the static tests did not form any precipitation. Thermal aging resulted in a color change for all tests, as expected, and the performance of the thermal-aged scale inhibitor was evaluated. This paper provides insight into the scale deposition and inhibition for fracturing treatments using seawater-based fluid at high-temperatures up to 300°F and furthers the effective strategies to address the scale issue during fracturing using seawater-based fluid.
Foamed acidic fluids have been utilized in the industry for enhanced oil recovery and fracturing applications due to their various advantages. Flowback enhancement, recovery of treatment fluids, and reduction of overall water consumption per operation are examples of these advantages. This study examines the utilization of a chelating agent, L-glutamic acid-N, N-diacetic acid (GLDA) in N2 and CO2 foamed fluids, which enhances the stability of foamed acidic fluids, lowers corrosion tendency, and is environmentally friendly. A modified high pressure and high temperature (HPHT) foam rheometer, and foam analyzer at ambient conditions, are used to test the acidic foamed fluids prepared in produced water using N2 and CO2. A screened out Alkyl diamine derivative surfactant has been tested at 212-300 °F and 1000 psi with and without GLDA. The effect of corrosion inhibitor addition on viscosity and foam quality is also investigated. Viscosity and foam quality measurements were done at increasing shear rates from 500 1/s up to 2000 1/s. Results showed that GLDA enhances the foamed fluid viscosity and stability. Resulted viscosities were in the range of 5 cP at higher shear rates to 25 cP in the lower shear rates region. Viscosity, in general, is lowered by higher shear rates, but foam quality is not affected. Fluid systems with a corrosion inhibitor also resulted in lower viscosities. The most stable and relatively higher viscosity values resulted from the 1 wt.% surfactant concentration with the addition of 15 wt.% GLDA and no corrosion inhibitor. Ambient conditions foam analyzer results showed higher foam height and half-life values of 182.8 mm and 16.5 minutes respectively when foaimg using N2 compared to 77.4 mm and 2.16 minutes when foamed with CO2. The addition of corrosion inhibitor showed significant negative impact in all cases, but least on the half-life of the CO2 foamed fluid. The rheology study provided did not consider the addition of thickeners which could be further investigated. This study covers the novel utilization of a chelating agent as an additive in CO2 and N2 acidic foamed fluids at harsh conditions. Furthermore, the fluid systems tested can be investigated and utilized as reliable stimulation fluid systems at temperatures up to 300 °F.
Summary This research fills the gap in understanding the impact of corrosion inhibitors (CIs) and a chelating agent on the rheology and stability of foam under harsh conditions. In this regard, a modified high-pressure, high-temperature (HPHT) foam rheometer and HPHT foam analyzer were used to investigate foam rheology and stability at 1,000 psi and 120 to 150°C with carbon dioxide (CO2) in the gas phase. Surfactant screening showed that Duomeen TTM and Armovis are thermally stable at high temperature and high water salinity and thus were used in this study. The liquid phase generally contained produced water (PW) (total dissolved solids ~ 24,611 ppm), 15 wt% chelating agent [L-glutamic acid-N, N-diacetic acid (GLDA)], and 1 wt% surfactant with and without a CI. First, we screened the viscosity and stability of Duomeen TTM and Armovis; the results showed that Duomeen TTM has a higher viscosity (at least by 82%) at a low shear rate, but both have similar viscosity at a higher shear rate. However, Armovis produced more stable foam. Once the GLDA was added to the Duomeen TTM solution, the viscosity increased significantly by 135% at a high shear rate (1,000–1,500). For the Armovis system, the viscosity improved by 77% and 68% at the low and high shear rates by adding GLDA. Additionally, foam stability was improved remarkably in both systems; half-life time almost doubled. Finally, we reported the effect of CI on the fluid systems, showing it considerably reduced the foam viscosity and stability. It reduced the half-life of the Armovis system by 79.4% and hindered the generation of foam for the Duomeen TTM system. A detailed discussion of foam properties, such as foamability, bubble count, and bubble radius, is provided. This study provides a wide-ranging understanding of additives’ impact on stimulating foam stability at HPHT.
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