Bacterial Nanocellulose as an Eco-Friendly Additive in Water-Based Drilling Fluids Applied to Shale Formations

S. DELL ELCE; EUGENIA TAVERNA, MARÍA; J. JOVI; VILLADA, YURANY; CASIS, N.; FORESTI, L.; DIANA ESTENOZ

Congreso; AIChE Annual Meeting; 2022

Drilling fluids are mixtures of natural andsynthetic chemical components used to cool and lubricate the bit and the drillstring, clean the hole bottom, carry cuttings to the surface, control formationpressures, among others. An efficient drilling fluid must also present severalcharacteristics, such as desirable rheological properties, fluid lossprevention, stability under high-temperature and high-pressure conditions, aswell as stability against contaminating fluids such as salt water, calciumsulfate, cement, and potassium. According to the nature of the continuousphase, fluids are classified into two main groups, water-based drilling fluids(WBMs) and oil-based drilling fluids (OBMs). OBMs are known to provide unequalledperformance but they are subject to environmental regulations. WBMs present lowenvironmental impact but exhibit some disadvantages associated with shaleinhibition, lubricity, and thermal stability. To avoid these drawbacks,specific additives can be added to deliver properties close to OBMs performancewhile minimizing the environmental impact.As nanotechnology has gained in popularity,lignocellulosic materials have been fractionated to the nanoscale where theircomponents can be separated and utilized in drilling applications. Thenanoscale dimension of cellulose, as well as its morphology, aspect ratio,surface chemistry and surface energy impart very distinctive properties whencompared to cellulose fibers, such as improved mechanical performance andthermal stability.Different raw materials and processes toisolate nanocellulose have been widely studied. From lignocellulose materialssuch as wood, cotton, linen, sugar cane, and agricultural wastes to evenbacteria and tunicates, nanocellulose has been effectively produced. Sourcesand choice of processing for nanocellulose production will directly impactspecific characteristics, such as morphology, aspect ratio, rheological andoptical properties, among others. The three main groups of nanocelluloses arecellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and bacterialnanocellulose (BNC). In this work, a sustainable alternative forthe design of WBMs with environmental and economic advantages for use in shaleformations is sudied. In particular, the replacement of XGD, a natural polymerwith viscosifying and viscoelastic properties that is stable over a wide rangeof temperature, salinity and pH, is investigated. Due to its chemicalstructure, low cost and environmentally friendly characteristics, BNC from glucose-sweetenedblack tea is proposed as an alternative for such replacement and theirperformance in WBMs are evaluated. The effects of WBMs components on theirstructural, rheological, filtration, and thermal properties are investigated.Additionally, the rheological properties of WBMs are also theoreticallydescribed using the Sisko model.The NCB was purified in alkaline solution andcharacterized. The NCB suspension in the form of nanoribbons (1.40% m/m) exhibiteda Z potential (at pH 7) of -9.79±1.68 mV. On the other hand, a high percentageof crystallinity (about 90%) was measured. The average viscosimetric degree ofpolymerization was 8181±1583, characteristic of bacterial celluloses. Inaddition, the thermal stability was good, with its maximum degradationtemperature close to 370 °C. The micrographs revealed that the nanoribbons havean average width of 76 nm.Subsequently, WBM systems containingpolyanionic cellulose (PAC) [0.50%], sodium bentonite (BT) [1.5%] and NCB orxanthan gum (XGD) [1-0.00; 2- 0.10; 3- 0.25; and 4-0.50%]. XGD-based WBMs wereused for comparison purposes. Their rheology and thermal stability wereevaluated. NCB-containing WBMs exhibited higher viscosities than thosecontaining XGD while thermal stability is similar for both fluids.