Evaluation of the inhibition capacity of chemical additives
to be used in drilling fluids environmentally correct
Danielly Vieira de Lucena*, Raquel Santos Leite, Cristiane Henrique da Silva, Luciana Viana
Amorim, Hélio de Lucena Lira.
Drilling fluids are indispensable to the well perforation industry, once they have important
functions, such as: (1) carry cuttings from the hole and permit their separation at the surface;
(2) cool andclean the bit; (3) reduce friction between the drillpipe and wellbore or casing; (4)
maintain the stability of the wellbore; (5) prevent the inflow of fluids from the wellbore; (6)
form a thin, low-permeable filter cake; (7) be non-damaging to the producing formation; (8)
be non-hazardous to the environment and personnel. When the perforation reach the
geological formations constituted of hydratable shale and it is viable the use of water base
fluids, it is necessary the use of inhibitors with the aim to avoid the incorporation of cuttings
from the hole, the swelling of the formation and collapse of the well wall (SERRA, 2003).
The inhibitors are intend to prevent or minimize, in a efficient way, the hydrate process and
consequently the swelling of the reactive clay and shale. The operation mechanism consist of
the fixation, by adsorption or effective chemical bond, of the cationic fraction in the negative
surface of clay and give “freedom” the original cation present in the claymineral. Potassium
chloride (KCl) and ammonium quaternary salts with chloride contra-ions are chemical
inhibitors widespread used in drilling fluids (SERRA, 2003).
Nowadays, due to the regulations proposed by environmental protection agencies, the
application of these inhibitors has been widely discussed and new products, without chloride,
had been developed.
The aim of this work is to evaluate the inhibition capacity of three chemical additives
(potassium sulphate, potassium acetate and potassium citrate), environmentally correct, to be
applied in the water base fluids to the petroleum industry. The inhibition capacity of the
additives was evaluated by method of Foster (1953) swelling using the sodium bentonit clay
with high degree of swelling. The additives were studied in different content (10, 12, 14, 16,
18 and 20g of inhibitors/350L of water). The results from the swelling test and the surface
response indicated that the selected inhibitors (potassium sulphate, potassium acetate and
potassium citrate) present best results when compared with commercial inhibitors (KCl and
“Kla Gard”). It was observed that the inhibitors, from the concentration of 16g/350mL of
water, inhibit entirely the swelling of the clay. Also it was confirmed that the best inhibitions
are reached by the use of inhibitors in combination (binary and ternary compositions).
Keywords: drilling fluids, swelling inhibitors, environment.
FOSTER, M.D., Geochemical Studies of Clay Minerals. (Ii) Relation Between Ionic
Substitution and Swelling in Montomorillonite, American Mineralogy 38, 1953, p. 994.
SERRA, A.C.S., A Influência de Aditivos de Lama de Perfuração Sobre as Propriedades
Geoquímicas de Óleos. Rio de Janeiro: Tese de doutorado-UFRJ. 2003. 163p.
*MSc Student in Material Science and Technology, CCT/ UFCG, R. Basílio Araújo, 886,
Catolé, Campina Grande –PB, e-mail: [email protected]