Influência da adição de terra diatomácea e hidrogel na reologia de fluidos de perfuração de petróleo constituídos de biopolímeros e bentonita no desempenho de cura de fraturas e invasão de filtrado

Abstract

Especially as the flow rate and differential pressure between the circulating fluid and the well increase, the fluid loss becomes more significant. Whether natural or artificial fractures and permeable rock, fluid invades formation in a phenomenon called loss of circulation. To reduce this problem, methods are needed to mitigate the loss of circulation. In this work, an experimental and theoretical study was carried out aiming to develop a single drilling fluid that minimizes the loss of circulation in the 2mm fractures and in the pore - filtration rock. This study was developed in stages: The first was the choice of the best polymer to compose the water-based fluid, F(X). These were prepared using different biopolymers (X) - xanthan gum (XG), carboxymethylcellulose (CMC) and Hydroxypropylstarch (HPS) and bentonite (BT) was used as a viscosifier. The Loss of Circulation (LCMs), diatomaceous earth (DE) and hydrogel (HG) materials were inserted into the F (X) fluid formulation to mitigate the loss of circulation. The fluids were designed with a density of 1.14g / cm3, pH ᵙ 8.5 and named as F (XG)DE-HG, F (CMC)DE-HG and F (HPS)DE-HG. Among fluids, F (CMC) DE-HG showed better affinity with LCMs. HG particle swelling, wide particle size distribution range, good thermal stability, conservation of suspended LCMs and unstable zeta (flocculated) potential at pH 8.5 were observed. The second step was choosing the best LCMs. For this, only the CMC biopolymer fluid was selected, as it presented typical characteristics of a noninvasive drilling fluid. From a complete factorial experimental design with 16 experiments, it was possible to infer that the CMC polymer at level +1 exerted the main effects in combating fracture circulation loss and filtration. The +1 level BT particles are also important. In addition, hydrogel LCMs had a significant effect, whereas the effect of TD LCMs was not significant to combat the loss of circulation. In the flow results, among the 16 fluids, only Fluid 12 (CMC +1, HG +1, DE -1 and BT +1) presented superior efficacy, since it sealed the 2mm fracture in 1 (one) minute test, In addition, a low filtrate volume was observed in the filtration, with a cake thickness of 0.09 cm. The third step was drilling fluid optimization. A new factorial design completes of 8 (eight) experiments and triplicate at the center point, without diatom earth, was named as WBA. Circulation loss was progressively decreased in filtration tests for all non-DE (WBA) fluids compared to diatomaceous earth fluids. In the fracture test, it was observed that the sealing occurred in the first half minute of the test. Of the 8 WBA fluids, only WBA 8 fluid (CMC, BT and HG at level +1) quickly blocked the fracture throat and showed minimal loss of filtration circulation.