Field Application of Glass Bubbles as a Density Reducing Agent in an Oil Base Drilling Fluid for Marginal/Low-Permeability/Low-Pressure Reservoirs

Abstract

This paper shows the results of a successful application of the addition of hollow glass spheres, also known as glass bubbles, as a density reducing agent in a drilling fluid. In this field application, glass bubbles were used in combination with an oil based drilling fluid (Core-Drill-N). It was corroborated that the fluid-glass bubble mix is stable, homogeneous, and is compatible with conventional mud motors, bits and surface cleaning equipment.. The system has good rheological and filtration control properties and is suitable for drilling low pressure reservoirs, low permeability and pay zones. During this field application in the well MOT-25B in Venezuela, the density of the base fluid was maintained between 7.1–7.3 ppg (near balance condition) with calcium carbonate as bridging agent. This technology is an alternative to the use of aerated fluids where the reservoir requires a fluid density between 6.0–7.5 ppg, offering some economical and technical advantages due to the elimination of surface compressing and air injection facilities, and to the simplification of operations required to avoid excessive overbalance during drillpipe trips. Additional potential benefits of this low-density fluid include torque reduction as a result of higher lubricity, higher penetration rates and decreased formation damage due to lower invasion of drilling fluid. Glass bubbles are also an alternative to decrease the density of water based drilling fluids, polymer-based fluids, emulsion systems and brines. Laboratory tests were also carried out with different concentrations of glass bubbles in order to evaluate potential field substitutes for aerated fluids in wells which might require lower density fluids. Several formulations for the systems mentioned above were developed with the purpose of achieving maximum density reduction without affecting some mud properties. Fluid density as low as 6.0 ppg was obtained from a 100% oil base mud. Introduction In the last few years in Venezuela there has been an increase in the drilling activities in low-pressures reservoirs with low-permeability, where the utilization of drilling fluids with a density higher to the required could result in a partial or complete loss of fluid into the formation. An excessive level of overbalance could cause effects such as an increase in drilling costs, potential fracturing of the formation, formation damage, and finally potential well loss. The drilling of the above mentioned depleted reservoirs require the use of lower density fluids with specific gravity less than 1 (8.33 ppg). These fluids, in principle would allow maximum extraction while minimizing damage to the producing formation. This work shows the results of the application of glass bubbles as a density reducing agent in an oil base drilling fluid under near balance conditions in an inclined well, drilled in Motatán field in Western Venezuela. Fig. 1 shows Motatán field, in Western of Venezuela. Motatán field is characterized by reactive shale, depleted formations and highly fractured reservoirs with high axial stresses, known for deferred oil production due to flushing by lost circulation. This reservoir has a typical range for matrix permeability from 50 to 100 mD. Porosity in this area is 14% approximately. In addition, this paper presents laboratory test results and the first field trial of the 100% oil system with mineral oil as the base and glass bubbles as the density reducing agent in a drilling fluid. The fluid was used for drilling the 8 1/2" section of MOT-25B well, with an estimated BHT of 250°F. MOT-25B was a deviated well. Drilling with this fluid began at 8275' and reached an Eocene objective at 10,100' (Misoa: B-0/B-4 sand). The density range was 7.1 ppg to 7.3 ppg with 15 ppb using calcium carbonate as bridging agent.

Investigation of Stability of Hollow Glass Spheres in Fluids and Cement Slurries for Potential Field Applications in Saudi Arabia

“…in India (Thyagaraju et al 2009). In areas of slow ROP, oil-based mud formulated with HGS successfully reduced drilling operation by 11 days in Venezuela (Blanco et al 2002). A study conducted by Chen and Burnett determined that HGS does not create additional damage to the formation's permeability (2003).…”

Investigation Of The Stability Of Hollow Glass Spheres In Drilling Fluids In Diverse pH Environments And Assessment Of Potential Field Applications In Saudi Arabia

“…Two crucial factors that regulate the success of field trials are the selection of appropriate surface equipment and the determination of the formation pressure profile (Blanco et al 2002). The pressure profile of Wasia formation must be carefully studied in order to sustain the hydrostatic pressure within the desired range.…”

“…Another field implementation was conducted in Motatan field west of Venezuela. The oil-based fluid formulated with HGS completed drilling 11 days faster than the conventional mud (Blanco et al 2002), which was the main objective of the trial. In addition to onshore applications, an offshore field trial attempting NBD in the depleted reservoirs of Mumbai High was proved successful (Raju et al 2009).…”

Preparation of Hollow Silica Spheres by Soft Template Method

“…The employment of HSS is shown not only in scientific fields but also in extensive industrial applications, such as water-, heat-and sound composite materials, light weight composite filler, catalyst carrier, buoyancy materials, pigments and drilling fluids. [1][2][3][4] Various processing techniques for making HSS have been developed, such as soft-template methods [5][6][7], hard-template methods [8,9], spray pyrolysis [10] and spray drying [11]. Soft-template methods are the simpler synthetic approaches for producing hollow shells and have attracted the attention in the past years.…”