Fluid Loss Control – Improvement for HTHP Wells

Abstract

Fluid loss control is often a consideration, if not a major engineering exercise, for a wellbore workover or completion operation. When the mix includes high bottom hole wellbore temperature, high reservoir pore pressure and high reservoir permeability and porosity, then the well killing operation can become very complicated. For these reasons many operations include mechanical means of fluid loss control, thereby achieving positive well control for a long period of time without the worry of reservoir damage by fluid invasion and kill fluid byproducts. However, there are some instances, such as tripping drill pipe or tubing in or out of a well, that mechanical tools are not applicable. Enter chemical fluid loss control. Often referred to as "fluid loss pills," chemical fluid loss control has been associated with everything from shredded newspapers to the latest biopolymers, which may carry carefully engineered bridging solids. While completion operations will hopefully not use bridging solids usually reserved for lost circulation while drilling, the point is that just about everything at hand on a rig location or in a laboratory has been tried as a fluid loss control agent. For most of these chemical fluid loss pills, the upper limit of endurance is 275°F (135°C), which is the melting point of processed starch commonly found in fluid loss pills. Also, most commercially available fluid loss pills lose temperature stability as fluid density is increased with water soluble salts. A new fluid loss control pill has been designed to provide effective fluid loss control for 24 hours at 300°F (149°C) in a fluid density up to 12.5 pounds per gallon (1.50 specific gravity). Introduction The emphasis placed on fluid loss control can range from no real concern whatsoever to a major engineering exercise requiring laboratory filtration measurements on actual cores under simulated reservoir conditions, then making return permeability measurements. One important driver in the amount of consideration given to fluid loss control is the location of the well, be it onshore or offshore. Offshore completions get a lot of attention because of safety regulations that mandate a full fluid column in the casing and tubing during the completion, and typical complexity of deviated, high permeability, multi-zone and sometimes multi-lateral wellbores. In an offshore environment you also have to factor in the value of rig time should fluid losses delay the completion process. Additional important factors are the reservoir properties, such as permeability, pressure and temperature. Traditional fluid loss control is achieved by one or more of the following:placing a very high viscosity polymer "pill", either cross linked or linear, across the fluid loss zone, 1, 2 orplacing a "pill" across the fluid loss interval that builds an external and/or internal filter cake.3 Though cross linked cellulose derivatives are gaining popularity, historically, the brunt of viscosity-controlled fluid loss control needs have been placed on the shoulders of linear HEC. Regarding the creation of external and internal filter cake for fluid loss control, the 1990's saw the introduction of specially engineered calcium carbonate bridging solids conveyed with a biopolymer/starch blend that has been coined a "drill-in fluid".4 The drill-in fluids are amongst the most efficient fluid loss control fluids in the oilfield, however, they are usually reserved for open hole completions due to the fear of acid wormholing through the filter cakes in perforations during typical acid cleanup treatments. A recent shift in well completion methodology in the Middle East has brought to light a void in effective fluid loss control for high pressure, hot and highly permeable wells. All these parameters can be relative terms, with different individuals defining their own standards according to what they are familiar with. Work has been done to meet a specific need in a 300–315°F (149–157°C) sandstone reservoir having natural fractures.

Investigation of different environmental-friendly waste materials as lost circulation additive in drilling fluids

“…The type of drilling fluid to be used on the field is to be decided based on a few criteria such as type of formation and conditions of drilling operations (country's regulations, etc.) (Dias et al 2015;Evans 2003). The composition of these fluids might vary from one another but the functions of the fluids remain the same.…”

Influence of modified starches composition on their performance as fluid loss additives in invert-emulsion drilling fluids

“…The characteristics of the geological formation and the well geometry determine the type of fluid to be used in a drilling operation [20]. The employment of invert-emulsion (W/O) fluids can be justified in situations in which aqueous fluids face technical and operational limitations, such as drilling in zones with reactive shales, evaporites (salt, anhydrite, carnallite) and corrosive formations, in wells with high temperatures and pressures (HTHP), directional or horizontal wells with extended reach, wells with angular gain, wells with small diameter (slim holes), and in the presence of formations bearing hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) [21,22].…”