Use of Ester as a Precursor to Clean Formate Drill-In Fluid Damage in Horizontal Wells

Abstract

Long horizontal and multilateral oil and gas wells provide an attractive option for maximizing reservoir contact. Formate-based brines have been used in drilling and completion operations for more than 10 years. Advantages of these fluids include high density, solid-free brines, better compatibility with XC polymer, starches, and less potential for formation damage. These advantages were reported in several previous publications.Filter cakes that are generated by drilling fluids can act as a barrier to the fluid flow in both cased and openhole wells. Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimizing leakoff rate. These solid particles become consolidated and trapped in a polymeric material, and this makes the filter cake a very effective permeability barrier.The conventional method for cleaning filter cake is by using solids-free formate brines, either by soaking or circulating for many hours at high flow rates. This mechanical technique removes only external filter cake. Chemical means like acids, oxidizers, chelating agents, enzymes, or combinations of these chemicals are usually used as an alternative method for dissolving both the external and internal filter cake. Most of these fluids cannot give a full coverage to the wellbore because of the formation heterogeneity.A new precursor (ester of an organic acid) can generate an acid downhole at a low release rate, which results in uniform fluid distribution through the wellbore. Compatibility and thermal stability tests between the precursor solution and formation brine were studied in detail. Return permeability experiments were conducted by using high-pressure/high-temperature (HP/HT) dynamic fluid loss cells. The ester solution was effective in cleaning the filter cake in comparison to the formate brines.A field application, where formate brine was used to drill and complete a gas producer in a sandstone reservoir, is included in this paper. The gas well was drilled in a weakly consolidated reservoir and was completed with expandable sand screens (ESSs). The bottomhole temperature was 285°F. The produced gas contained 2-3 vol% carbon dioxide and no hydrogen sulfide. Full analysis of flowback samples indicated that most of the returned solids were calcium carbonate. Laboratory tests indicated that the ester solution can be used to restore well productivity by removing damage induced by the drilling mud filter cake.

Minimizing Formation Damage in Drilling Operations: A Critical Point for Optimizing Productivity in Sandstone Reservoirs Intercalated with Clay

“…RDFs, also sometimes called drilling fluids, can be utilised in the drilling of hydrocarbonbearing formations or pay-zones [10,105], while completing fluids are utilised for completing and workover operations [105]. Drilling fluids are specially formulated to optimise the productivity index of the producing well [10,[105][106][107]. Currently, in the petroleum industry, the use of clear, heavy brine to drill the reservoir section is becoming very popular [105].…”

Development of the Natural Vegetable Gum Drilling and Completion Fluids System for Industrial Intelligent Application

“…Only one or a few vegetable gum as the primary treatment agent, and a number of polymers and the corresponding chemical treatment agent are added in the natural vegetable gum drilling fluid and completion fluids system. For the good adhesion, rheology and lubrication, this fluid system is commonly used in the gas and oil exploration engineering field without impairment to the environment [7][8]. As the maintenance of the system is convenient, non-toxic, and biodegradable, the natural vegetable gum drilling and completion fluids system is conducive to environmental protection.…”

Natural Vegetable Gum Drilling and Completion Fluids System for Industrial Control and Application

“…A number of polymers and the corresponding chemical treatment agent, with some vegetable gum as the primary treatment agent, are added in the natural vegetable gum drilling fluid and completion fluids system. The system is commonly used in the gas and oil exploration engineering field without impairment to the environment for the performance of the good adhesion, rheology and lubrication [8]. As the maintenance of the system is convenient, non-toxic, and biodegradable, the natural vegetable gum drilling and completion fluids system is conducive to environmental protection.…”