The First Experience of Formate Based Drilling Fluids Application in Russia

Abstract

Summary Notwithstanding significant advantages of the oil-base mud systems, their application inherent in a number of disadvantages that have been primarily attributable to environmental restrictions. In 2017 AKROS LLC and GAZPROMNEFT ran full-scale field-testing of potassium and sodium formate mud systems enabling them to analyze the performance of such systems and define the key application features. Conclusions on the application features of these systems and their perspectives in Russia are based on the results of the work performed. To implement potassium and sodium formate drilling fluids in GAZPROMNEFT fields, the full-scale laboratory testing was performed. The outcomes enabled the identification of fluid formulations for field applications and procedures for the maintainance of mud properties when drilling. Two intervals on «Gazpromneft-Khantos»' LLCs Yuzhno-Priobskoye Field and three intervals on «Gazprom Neft Shelf» LLC's Prirazlomnoye Field were drilled with potassium formate-base formulations. Field testing proved the high efficiency of potassium formate mud systems allowing them to: –achieve high drilling performance indicators;–gain experience in horizontal well drilling without lubricating additives demonstrating loads and torques similar to or lower than values observed in mud systems treated with lubricants;–develop the procedure for interval treatment of a high-density drilling fluid;–confirm the possibility of achieving a high density up to 1.41 g/cm3 without barite;–implement the technology ensuring mitigation of environmental risks connected with drilling fluids;–drill horizontal section and production casing intervals using one type of drilling fluid instead of two, facilitating reduced waste and prepared volumes. The potassium formate mud system proved to be efficient and has impressive perspectives in Russia as an alternative to oil-base drilling fluids, particularly for high formation pressure drilling. Based on field application results, practical application procedures and optimum recommendations for controlling mud properties were developed. Comparative tests for inhibition effectiveness, reducing friction factor, achieving high drilling performance were conducted.

Investigation of Non-Linear Rheological Characteristics of Barite-Free Drilling Fluids

“…With such fluid, as a rule, lower rheology, ECD and pressure losses in the well will be provided in contrast to traditionally used oil-based mud. It contributes to increasing drilling efficiency, especially in conditions of the narrow mud window [14,15,41]. It is also worth noting that the analysis of scientific literature proves that formate drilling systems are compatible with formation fluids, which creates conditions for increasing MPR and decreasing the contamination of bottomhole.…”

“…Density, g/cm 3 Sodium Zinc bromide-based solutions can provide the highest density among other salts (Table 1) but are much more corrosive than chloride-and formate-based solutions [13][14][15].…”

“…Formate-based drilling fluids are used in the North Sea as well as in other parts of the world, including Canada, Texas, the Gulf of Mexico, Argentina, Ecuador, Venezuela, Indonesia, Malaysia and Kazakhstan. Despite the fact that formate drilling systems are widely used outside the Russian Federation, it was only in 2017 that AKROS LLC and Gazpromneft PJSC carried out successful field tests using these drilling fluids at Yuzhno-Priobskoye and Prirazlomnoye (Pechora Sea shelf) fields [15]. Two horizontal sections were drilled with a formate-based solution in the Yuzhno-Priobskoye field.…”

Dependence of the Equivalent Circulation Density of Formate Drilling Fluids on the Molecular Mass of the Polymer Reagent

“…The solution is characterized by a high density with or without a low solids content. This, as a rule, will provide a lower ECD and pressure loss in the well compared to the traditionally used oil-based mud, which contributes to an increase in the efficiency of drilling, especially in the conditions of a narrow safe corridor in terms of density [13][14][15]. It is also worth noting that the analysis of the scientific literature proves that formate drilling systems are compatible with formation fluids, which creates preconditions for an increase in ROP and a decrease in NBHZ contamination [16][17][18].…”

“…Experience [14][15][16]23,24] with the use of fluids based on the salts of formic acid (formates) is presented in Table 1. In the solutions presented, compositions of polymeric reagents were used as a structure builder.…”