Application of Aphrons Technology in Drilling Depleted Mature Fields

Abstract

Depleted zones are intrinsic to most mature reservoirs throughout the world. The associated issues of effective, safe and economically viable well construction, completion and workover within low pressure environments become more challenging on a daily basis. This paper discusses the application of aphron drilling fluid technology, which offers a unique alternative option that can significantly improve the operational and economic aspects for continued development of these marginal assets. The authors will detail the development of the unique micro-bubble technology and its successful application in a mature and depleted field in Mexico. Introduction When formation pressures are drawn down, the type and severity of critical operating issues are exacerbated with few solution options. When taken in combination, the operator is often faced with substantially increased costs and risk, particularly where HSE issues are concerned. The problems associated with the pressure variances encountered in mature fields, coupled with the limitations of conventional fluid and equipment technologies to properly provide an equitable solution, have driven the need for a new approach to drilling and workover operations within depleted reservoirs in mature fields. One of the latest approaches to this dilemma is the use of the aphrons drilling fluid technology. In hundreds of wells in diversified applications worldwide, the aphron technology has proven to be a viable solution within these difficult parameters. Field experience has shown that even annular pressures exceeding depleted reservoir pressures by "several thousand" psi has not hindered the creation of the micro-environment seal and mitigating invasion. This feature alone has allowed operators to eliminate casing strings, safely workover highly depleted wells and even drill into normally pressure plays on wells with existing depleted production. All of this has been affected without compromising production. Because the seal is internal to the reservoir (Fig. 1), conditions for differential sticking do not exist. In many parts of the world, this feature has successfully enabled high-angle and horizontal well construction of highly depleted reservoirs using conventional equipment. No other fluids technology in the industry enables these types of operations. Since standard wellsite fluid mixing equipment is all that is required to employ the technology, it is highly compatible with normal wellsite operations. As a drilling, completion or workover fluid, the aphron technology functions as the backbone of the operation. Serving as the bridging technology between the difficult operating parameters of mature fields and the limits of conventional equipment when employed to develop these depleted reservoirs, the aphron technology offers a solution for prolonging the economic life of these assets. Statement of Theory and Definitions Aphrons1 (micro-bubbles) are incorporated into a specifically engineered base fluid2 to aid in mitigating losses in depleted / highly permeable zones. These micro-bubbles differ significantly from aerated fluids and foams. Aphrons do not coalesce. Upon entering the lower-pressure region within a depleted formation, aphrons remain discrete, yet will agglomerate to create a stable, but easily removed, internal seal called a "micro-environment".3 Because affecting this seal requires a higher annular pressure than that of the reservoir, it readily cleans up with reservoir flow-back as production is initiated. Synergies between the various features of the technology serve to minimize fluid invasion. The easily engineered high-LSRV (low-shear-rate viscosity) properties of the base fluid are achieved with high-yield, stress-shear-thinning (HYSST) polymers. This promotes design capabilities that are well suited for optimizing diversion of annular pressures away from the depleted formations, thus minimizing whole fluid invasion. The surfactant package and the associated "meniscus-wrapping theory"1,4 provide additional invasion control. The "energized-environment"4,5 associated with aphrons employed to form the internal "micro-environment" solids-free seal and the resultant localized increase in LSRV also contributes to mitigating invasion.

Application of Treatment for Deep Hole Drilling Debris in Gas-Rich Soft Coal Seams

“…(1)The adversary aspects, including unsatisfactory deep drill hole debris disposal, the rough drill hole wall at the soft and loose coal seam, difficulties in debris disposal, and other limitations existing in the downward drilling technology of coal mines, were all considered in this experimental study. In addition, debris disposal technology was optimized to ensure that the effective drilling depth could conform to technical requirements, thereby improving the effective utilization rate of drill holes (2)The magnet powder commonly used in beneficiation and mineral processing was selected as the suspension for debris disposal in the drill hole. This selection was based on the fundamental properties of the drilling debris in the drill hole of the coal mine as well as the characteristics of the existing suspending agents combined…”

“…The problem is that the borehole could produce more drilling debris during gas extraction when the stress is con-centrated on the coal seam, thereby resulting in low gas extraction efficiency. Failed disposal of residual drilling debris in the drill hole will not only make it challenging to utilize the borehole completely but also hinder gas migration and block holes of the casing pipe, which will become serious under ponding conditions [1][2][3][4]. In addition, residual drilling debris in the drill hole will result in nonuniform negative pressure of extraction, reducing the radial scope of gas extraction to a certain degree, aggravating the formation of hole collapse, and degrading the gas extraction effect.…”

Mathematical modeling of Aphron drilling nanofluid driven by electroosmotically modulated peristalsis through a pipe

“…Ehsan et al [12] investigate the rheological characteristics of aphron-based drilling fluids and reported that the rheology of such fluids can be more accurately described by Herschel-Bulkley fluid model. Some investigations in this direction revealed that aphron drilling fluids can be efficiently utilized in oil fields for drilling in the depleted formation with a very small loss of drilling fluids due to the presence of stabilized aphron [8,14,25] The application of aphron drilling fluid in reducing the formation damages during the drilling of horizontal wells is reported in [9].…”

Salt Effects on Formation and Stability of Colloidal Gas Aphrons Produced by Anionic and Zwitterionic Surfactants in Xanthan Gum Solution

“…CGAs have been frequently used as drilling fluid for depleted fractured formations. Their ability to survive longer at higher pressures in comparison to regular foams as well as easy production and easy handling have made them a suitable choice for drilling engineering [3][4][5][6][7][8][9][10][11]. From the review article [10], it can be seen that many papers have studied the effect of different parameters, including stirring time and speed, surfactant and polymer type, and concentration, etc., on the formation, stability, and performance of CGAs.…”