Low Impact Drilling Fluid for Deepwater Drilling Frontier

Abstract

One of the biggest challenges when drilling in deep water is the excessive dependence of drilling fluid rheological properties on temperature. Conventional drilling fluids often have high viscosity at the seabed temperature, which increases the Equivalent Circulating Density (ECD) and surge pressures when running pipe or initiating circulation, elevating the risk of fracturing the wellbore. This paper describes the development of a drilling fluid for deep-water applications, with minimum viscosity variation with temperature. Multiple laboratory formulations were evaluated during the development of the new, non-aqueous based drilling fluid that meets deep-water's challenging rheological and barite suspension requirements. CaCl2 brine was used as the internal emulsion phase, and synthetic isomerized olefin as the base oil. The testing followed the API Recommended Practice for Field Testing Oil-based Drilling Fluids. Samples were aged at dynamic conditions for 16 hours at several temperatures. Then, rheological properties and high-pressure high-temperature (HPHT) fluid loss, emulsion stability, and dynamic sagging were tested. Static sag experiments were also carried out for up to seven days together with improved step down rheology tests. A low-impact, non-aqueous drilling fluid (LIDF) was designed to minimize ECD increases by reducing the effect of cold temperature on the fluid viscosity. The fluid offers a superior low viscosity profile and rapid-set, easy-break gel strengths, while maintaining low shear rate viscosity at high temperatures with optimal weight material suspension. The fluid is also compatible with all contaminants usually found during the drilling operation and meets all the regulatory requirements for the Gulf of Mexico and other deep-water operational areas. Field application demonstrated that LIDF reduced the effect of temperature on the fluid rheological properties and minimized the risk of induced formation losses. These same rheological features reduced non-productive time associated with cement displacement and barite sagging. Supporting laboratory and field data are presented to demonstrate the superior performance of the fluid in maintaining rheological and barite suspension properties over a wide range of temperatures. The properties of the LIDF are achieved by matching the effects of emulsifier, organophilic clay, and rheological modifiers to maintain correct rheological properties at low and high temperatures.

Developing a Thermally Stable Ester-Based Drilling Fluid for Offshore Drilling Operations by Using Aluminum Oxide Nanorods

“…Since a low PV and a high YP BP is desirable, the T2.6N1 sample, with a 1 wt% NP concentration, exhibited the optimum PV/YP BP value in low temperature conditions in comparison to the LIDF. The gel strengths at 10 s and 10 min did not experience a jump from 10 s to 10 min, as compared to the LIDF reported by Kakadjian et al [43]. It should be noted that the samples demonstrated thermal stability, as they did not break at 70 °C, and showed a steadiness in the shear stress.…”

“…Other rheological properties of the nano-enhanced drilling fluids were investigated, as shown in Figure 8. It displays a comparison of the rheological properties of the nanoenhanced ester-based drilling fluid (EBDF) from this study with a commercial low-impact drilling fluid (LIDF) reported by Kakadjian et al [43] at an LT of 4.4 °C. The PV remained almost unchanged up to a 1 wt% NP concentration, while the YPBP showed a significant increase at 1 and 1.5 wt% NP concentration.…”

Nanomaterial-Based Drilling Fluids for Exploitation of Unconventional Reservoirs: A Review

“…Moreover, excessive surge pressure and swab can occur with little increases in colloidal-size drilled solids. Additionally, these solids improve the rheological properties of the fluid [92]. However, levels below the acceptable values of rheological properties can cause other problems such as inadequate hole cleaning, segregation of weighting material, and an inconsistent density profile in the annulus which leads to loss of drilling fluid or problems of well control.…”

Low Equivalent Circulating Density Organoclay-Free Invert Emulsion Drilling Fluids

“…This increased tendency to sag has been attributed to the limited gel network between the organophilic clays and the invert emulsion internal phase especially at higher temperatures [5]. Conventional drilling fluids have several limitations for offshore applications such as generation of excessive progressive gels strengths in static conditions, high viscosity, and high gel strength at low temperatures, but not enough yield point (YP) and low shear values at high temperatures [6]. Thus, the use of organoclay-based invert emulsion drilling fluids having the right rheology profile to give long-term stability as well as better ECD management in HPHT wells has been difficult.…”