High pressure and high temperature (HPHT) wells especially those with narrow pore / fracture pressure gradient margins present challenges in drilling. Maintaining optimum and low rheology for such wells becomes a challenge where a slight change in the bottom-hole pressure conditions can lead to non-productive time. However maintaining low viscosity profile for a drilling fluid can pose a dual challenge in terms of maintaining effective hole-cleaning and barite-sag resistance. This paper describes the formulation of 95pcf medium-density organoclay-free invert emulsion drilling fluids (OCIEF). These fluids were formulated with acid-soluble manganese tetroxide as weighting agent and specially designed bridging-agent package. The fluids were hot rolled at 300°F and their filtration and rheological properties were measured. The paper describes the static-aging, contamination, HTHP rheology measurements and filter-cake breaking studies of the fluids at 300°F. Particle plugging experiments were performed on both the fluids in order to determine the invasion characteristics and the non-damaging nature of the fluids. These organoclay-free invert emulsion fluids were then field-trialed in different wells with good results. The OCIEFs showed optimum rheology and filtration properties. The fluids gave lower PV, which ensured that the fluid presents low ECD contribution while drilling/circulating. Sag factor analysis for the fluids after static aging for 24 and 48hours showed excellent stability and minimal sag propensity. HTHP rheology showed that the fluids had consistent PV and YP values across a range of temperatures and pressures. Contamination studies showed that the effect of contaminants on the organoclay-free fluid was minimal and any change in properties can be easily controlled using conventional treatments. The paper thus demonstrates the superior performance of the developed fluid in achieving the desired lab and field performance. Field deployment of the 95pcf organoclay-free invert emulsion fluid helped to maintain the required hole stability in the HTHP well. The well was displaced to 95pcf production screen test (PST) fluid and completed with a 4 ½" sand screen.
High pressure and high temperature (HTHP) wells especially those with narrow pore / fracture pressure gradient margins present challenges in drilling. Maintaining optimum and low rheology for such wells becomes a challenge where a slight change in the bottom-hole pressure conditions can lead to non-productive time. However, maintaining low viscosity profile for a drilling fluid can pose a dual challenge in terms of maintaining effective hole-cleaning and barite-sag resistance. This paper describes the formulation of 95pcf medium-density organoclay-free invert emulsion drilling fluids (OCIEF) with a low viscosity profile. The fluids gave lower plastic viscosity (PV), which ensured that the fluid presents low equivalent circulation density (ECD) contribution while drilling/circulating. These fluids were formulated with acid-soluble manganese tetroxide as weighting agent and specially designed bridging-agent package. The fluids were hot rolled at 300oF and their filtration and rheological properties were measured. The paper describes the static-aging, contamination and high pressure/high temperature rheology measurements of the fluids at 300oF. Particle plugging experiments were performed on the fluids to determine the invasion characteristics and the non-damaging nature of the fluids. These organoclay-free invert emulsion fluids were then field-trialed in different wells with good results. Field deployment of the 95pcf organoclay-free invert emulsion fluid helped to maintain the required hole stability in the HTHP well. The paper demonstrates the superior performance of the developed fluid in achieving the desired lab and field performance.
The present paper describes the results of the formulation of an acid-soluble low ECD organoclay-free invert emulsion drilling fluid formulated with acid soluble manganese tetroxide and a specially designed bridging package. The paper also presents a short summary of field applications to date. The novel, non-damaging fluid has superior rheology resulting in lower ECD, excellent suspension properties for effective hole cleaning and barite-sag resistance while also reducing the risk of stuck pipe in high over balance applications. 95pcf high performance invert emulsion fluid (HPIEF) was formulated using an engineered bridging package comprising of acid-soluble bridging agents and an acid-soluble weighting agent viz. manganese tetroxide. The paper describes the filtration and rheological properties of the HPIEF after hot rolling at 300oF. Different tests such as contamination testing, sag-factor analysis, high temperature-high pressure rheology measurements and filter-cake breaking studies at 300oF were performed on the HPIEF. The 95pcf fluid was also subjected to particle plugging experiments to determine the invasion characteristics and the non-damaging nature of the fluids. The 95pcf HPIEF exhibited optimal filtration properties at high overbalance conditions. The low PV values and rheological profile support low ECDs while drilling. The static aging tests performed on the 95pcf HPIEF resulted in a sag factor of less than 0.53, qualifying the inherent stability for expected downhole conditions. The HPIEF demonstrated resilience to contamination testing with negligible change in properties. Filter-cake breaking experiments performed using a specially designed breaker fluid system gave high filter-cake breaking efficiency. Return permeability studies were performed with the HPIEF against synthetic core material, results of which confirmed the non-damaging design of the fluid. The paper thus demonstrates the superior performance of the HPIEF in achieving the desired lab and field performance.
This paper describes the success of using a new low ECD OCIEF in different Gas Reservoirs at elevated temperatures and with differential pressures up to 4,500 psi. The objective of the paper is to highlight the superior performance of OCIEF during the execution which led in overcoming challenges in such type of environment without compromising performance This paper describes several applications where the OCIEF has been deployed achieving optimum drilling performance while minimizing the formation damage of the reservoir. Consequent applications showed how the implementation of work methods, best practices and optimized drilling parameters allowed to successfully drill the section without downhole problems and pass the Production Screen Test (PST) and finally allow a proper clean-up while producing the well. Initial deployment of the fluid system shows the required fluid specifications to properly address the slim hole challenges in high overbalance environment. Field implementation and continuous fluid performance improvements are reported in this paper, showing how the fluid system helped to successfully complete numerous wells in different fields. The versatility of the fluid system in terms of rheological profile and thermal stability and the minimized formation damage characteristics made the OCIEF as the sole non- aqueous fluid solution applied in Gas Reservoirs under extreme overbalance conditions. No more non- productive time has been experienced over the entire drilling campaign performed with OCIEF. The new low ECD OCIEF (Organophilic Clay Free Inverted Emulsion Fluid) designed a new and enhanced polymer package, without organophilic clay and lignite and with acid soluble manganese tetroxide as weighting agent replaced the usage of water-based fluids without compromising production and with improved performance in extremely challenging gas wells. The proven performance is opening more boundaries for future applications in similar wells.
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