Drilling high pressure wells in the Khursaniyah field, Saudi Arabia, has become a challenge due to the high pressure flow from Base Jilh Dolomite formations coupled with loss circulation across the depleted Upper Jilh formations in the 8 3/8" section. The variations in formation pressure across these layers have led to issues like well flowing, losses, and stuck pipe causing considerable nonproductive time. This paper analyzes the historical problems encountered in the offset wells to identify the critical fluids related issues during drilling of this section: Thermal and pressure stability of fluids additives.Downhole pressure management.Differential sticking or induced losses.Low contamination tolerance to formation fluids influx.Barite sagging.Rheology and free-water management. This paper also discusses laboratory customization of optimized high-density fluid formulations and field handling guidelines to drill this critical 8 3/8" section and minimize fluid associated risks. The fluid was modeled to have as low a rheology and gelation profile as possible while suspending weight material by understanding the pressure envelope, bore-hole strength, torque, and drag constraints in combination with the fluid rheology and density relationship under the influence of anticipated drilling practices. The field application on this customized formulation with engineering observance was successful to drill this critical section and the case study for such well is presented in the paper.

Formation damage is a by-product of drilling, completion and production process and is attributed to many factors. In open-hole (OH) and cased-hole (CH) wells, hydrocarbon flow may be impeded by various damaging mechanisms caused by drilling and completion fluids, in-situ emulsions, water block, organic deposition and oily debris left downhole. Mesophase fluids have been successfully developed to effectively resolve the persistent problem of near-wellbore damage. The physical-chemical properties of the mesophase systems include high oil solubilization, high diffusion coefficients through porous media and the reduction of interfacial tension between organic and aqueous phases to near zero, making them excellent candidates for removing formation damage. The chemistry of mesophase fluids makes the systems excellent choices for superior synthetic or oil-based mud (S/OBM) displacements in casing and for OBM filter cake cleanup in open-hole completion applications. Mesophase fluids are thermodynamically-stable, optically transparent solutions composed of two immiscible fluids. They differ from ordinary emulsions because they can be prepared with little or no mechanical energy input. They are typically composed of a non-polar or oil phase, an aqueous phase, surfactant(s) and an optional co-surfactant. Depending on how they are formulated, they can exist in a single-phase or in a three-phase system, in which the middle-phase microemulsion is in equilibrium with excess water and oil. The formulation characteristics, phase type, and ultimately, the cleaning efficiency of a microemulsion is dictated by the hydrophilic-lipophilic balance between the surfactant(s) and the physico-chemical environment. The microemulsions described in the study are single-phase where oil and water are co-solubilized by the surfactant(s) and co-surfactants. The water/oil interface has a zero or near-zero curvature, indicative of the bicontinuous phase geometry that produces very low interfacial tension and the rapid solubilization of oil upon contact. The formation of a mesophase does not ensure the fluid will solubilize oil effectively to leave surfaces water-wet. The mesophase behavior and cleaning efficiency can be altered by salinity, surfactant, co-surfactant, oil type, temperature and particulates. No two wells are identical and the physical and chemical conditions can vary greatly depending on the application. As a consequence, robust, optimized formulations are necessary and validation testing is required to determine the efficacy of a mesophase for a specific application, i.e., OBM displacement/cleanup and removal of formation damage in open-hole and cased-hole wells. This paper presents a technical overview of mesophase technology and field applications that demonstrate the efficiency of mesophase fluids for removing S/OBM debris and filter cakes, reducing near-wellbore damage and improving well productivity.

The use of water based mud (WBM) in drilling applications under extreme Pressure and temperature has been increasing rapidly in the drilling industry over the past few years. It is now more crucial to close the technological gap that presents challenges towards developing high Density water based mud systems for High Temperature High Pressure (HPHT) wells. These challenges include rheology control, weighting agents sagging tendencies associated with high down hole temperature, In addition to the high solids loading which limits the free water availability impacting polymers performance and therefore, rheology, HPHT fluid loss and filter cake thickness control become an issue that requires special optimization and extra field maintenance. Operating under narrow margin between pore pressure and fracture initiation pressures adds to the complexity of the drilling fluids maintenance where a slight change in the bottom hole pressure (BHP) could lead to significant increase in the non-productive time "NPT" due to the time spent in solving possible fluid losses and kicks. This paper discusses the outstanding performance achieved in a deep HPHT formation drilled using water base mud weighted with Manganese Tetroxide (Micromax)/Barite blend, from planning and extensive lab testing to field implementation. This paper also describes and compares the methodology of using Micromax/Barite versus using barite only as the weighting agent and finally the field results.

Formation damage is one of the main concerns at various stages of drilling, completion and production processes and is attributed to many factors. Either in open-hole or cased-hole completed wells, hydrocarbon flow in the reservoir may be impeded by various damaging mechanisms such as in-situ emulsions, water block, organic deposition and oily debris left downhole. Micro-emulsion fluids are thermodynamically stable, optically transparent solutions of two immiscible fluids formulated with a specialized surfactant blend and/or co-surfactant. They differ from normal emulsions because they can be prepared with little or no mechanical energy input. They typically comprise a non polar (oil) phase, a polar (aqueous) phase, surfactant(s) and an optional co-surfactant. Depending on how they are formulated, mesophase fluids can exist in a single-phase or in a three-phase system wherein the middle-phase microemulsion is in equilibrium with excess water and/or oil. The formulation characteristics, phase type, and ultimately, the cleaning efficiency of a microemulsion are dictated by the hydrophilic-lipophilic balance between the surfactant(s) and the physico-chemical environment. The microemulsions described in this study are single-phase where oil and water are co-solubilized by the surfactant(s) and co-surfactants. The water/oil interface has a zero or near-zero curvature, indicative of the bicontinuous phase geometry that produces very low interfacial tension and the rapid solubilization of oil upon contact. The formation of a micro-emulsion alone does not ensure the fluid will solubilize oil effectively to leave surfaces water-wet. The micro-emulsion behavior and cleaning efficiency can be influenced by salinity, surfactant, co-surfactant, oil type, temperature and particulates. No two wells are identical and the physical and chemical conditions can vary greatly depending on the application. As a consequence, robust, optimized formulations are necessary and validation testing is required to determine the efficacy of a mesophase for a specific application, i.e., OBM displacement/cleanup and removal of formation damage in openhole and cased-hole wells. Micro-emulsion fluids were successfully developed to effectively resolve the persistent problem of near-wellbore damage. The physico-chemical properties of the micro-emulsion systems include high oil solubilization, high diffusion coefficients through porous media and the reduction of interfacial tension between organic and aqueous phases to near-zero, making them excellent candidates for removing formation damage. The chemistry of micro-emulsion fluids makes the systems excellent choices for superior synthetic or oil-based mud (S/OBM) displacements in casing and for OBM filtercake cleanup in openhole completion applications. This paper presents a technical overview of micro-emulsion technology and field application in a high- temperature gas environment that demonstrate its efficiency in removing Non-Aqeuous Fluid (NAF) debris and filter cakes, whilst reducing near-wellbore damage and improving well productivity and solids mobility.

Minimizing formation damage is an important parameter to be considered to have expected production rates. Formation damage can happen at any phase during drilling, completion or production and is attributed by too many factors. Formation protection is critical while drilling the production zone because damage to the formation can adversely affect the well's production potential. This pay zone damage is minimized with the use of drill-in fluids, specialized fluids for "drilling in" and protecting oil/gas production formations. Damage to the pay zone, including fine solids migration into the formation permeability channels, in-situ emulsions, water block, organic deposition, oily debris, clay swelling within the formation pore spaces and irreversible reactions with invading polymers, reduce the average permeability of the formation, resulting in lower production rates. Most formation damage caused by conventional drilling fluids is by fluid invasion containing barite, finely ground drill solids and/or weighting material. The formation damage is even more critical in horizontal/inclined wells where the reservoir exposure is more and production rates are high. Micro-Emulsion fluids are thermodynamically stable, optically transparent solutions comprising two immiscible fluids. They differ from ordinary emulsions because they can be prepared with little or no mechanical energy input. Micro-Emulsions typically comprise a non-polar or oil phase, a polar or aqueous phase, surfactant(s) and an optional co-surfactant. Depending on how they are formulated, micoemulsions can exist in a single-phase or in a three-phase system, in which the middle-phase microemulsion is in equilibrium with the excess water and oil. The formulation characteristics, phase type, and ultimately, the cleaning efficiency of a microemulsion are dictated by the hydrophilic-lipophilic balance between the surfactant(s) and the physico-chemical environment. The microemulsions described in the study are single-phase where oil and water are co-solubilized by the surfactant(s) and co-surfactants. The water/oil interface has a zero or near-zero curvature, indicative of the bicontinuous phase geometry that produces very low interfacial tension and the rapid solubilization of oil upon contact. The Micro-Emulsion behavior and cleaning efficiency can be altered by salinity, surfactant, co-surfactant, oil type, temperature and particulates. A robust, optimized formulation is necessary and validation testing is required to determine the efficacy of a micro-emulsion for a specific application, i.e., OBM displacement/cleanup and removal of formation damage in openhole and cased-hole wells. Micro-Emulsion fluids were successfully developed to effectively resolve the persistent problem of near-wellbore damage. The physical-chemical properties of the micro-emulsion systems include high oil solubilization, high diffusion coefficients through porous media and the reduction of interfacial tension between organic and aqueous phases to near-zero, making them excellent candidates for removing formation damage. The chemistry of Micro-Emulsion fluids makes the systems excellent choices for superior synthetic or oil based mud (S/OBM) displacements in casing and for OBM filter-cake cleanup in openhole completion applications. This paper presents a technical overview of micro-emulsion technology and field applications that demonstrate the efficiency of Micro-Emulsion fluids for removing S/OBM debris and filter cakes, reducing near-wellbore damage and improving well productivity.