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.

Formation damage is a by-product of drilling, completion, and production process and is attributed to many factors. In openhole (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 openhole 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 openhole 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.

Unconsolidated reservoirs usually have poorly arranged sand formations. Consequently, produced hydrocarbon fluids may carry sand during the flow through screens to the surface. Unconsolidated sandstone reservoirs are highly prone to sand production, particularly during the initial stages of production, or when the reservoir pressure has dropped, or at the early onset of water. This sand production could lead to serious reservoir damage, adversely affect production, and reduce the potential production life of the reservoir. Common problems associated with sand production include erosion of downhole and surface equipment, collapse of the formation, and handling and disposal of the produced sand, particularly on offshore platforms. Operators around the world spend millions of dollars in sand cleaning workover operations. In addition to current conventional sand control techniques, a novel sand control completion technology that uses a shaped-memory polymer (SMP) is actively deployed. When exposed to a catalyst, this polymer expands to conform to the wellbore sand face. The result is a porous and permeable filtration device that prevents the issues mentioned above and ensures production levels are maintained, maximizing the reservoir's potential. This outstanding technology offers a superior alternative to conventional sand control methods while reducing operational risk, cost and time by achieving total conformance and superior filtration on every job. The SMP is deployed in a compact state in the well and is activated by temperature and catalyst downhole to an expanded state that conforms to the shape of the wellbore. The SMP provides improved wellbore stability and efficient sand control, regardless of the wellbore irregularity across the formation sands in different reservoir zones. This technology can be considered for standalone sand control or used in combination with inflow control devices (ICDs), to ensure production optimization in a horizontal well. Operationally, it is critical to ensure that the activation fluid used as catalyst for the SMP provides a rate of expansion best suited for field operations. For this particular application, it was also essential that the activation fluid should be non-damaging to the reservoir, compatible with the oil-based mud (OBM) drilling and completion fluids used to suspend the well, and operationally as well as environmentally friendly. Several fluid combinations were tested to identity the suitable catalyst that triggers the activation of the shaped-memory polymer and completes expansion at a rate desired for field operations. The optimum fluids are based on micro-emulsion technology that are environmentally friendly and able to activate the SMP fully within a stipulated amount of time (8 to 12 hours). The added benefits include breaking the oil-based filter cake and maximizing dispersion and flowback when the well starts producing. This paper details the lab testing performed on SMP with various fluid mixtures and outlines the benefits observed using the mesophase fluid. This approach for improved sand control enables the operator to save all the workover-related expenses that are caused by sand production.

Drilling and completing reservoir formations without causing the formation damage is nearly or almost impossible. In most of the cases, selected drilling or completion fluids that were selected during different phase of the operation while drilling and completing the well causes this damage and act as a barrier for the reservoir’s flow leads to low production levels. Drilling or completion fluid can cause the formation damage due to poor design and selection of the fluid, not having sufficient data on reservoir characterstics, availability and feasibility of the chemicals. Recent studies shown, most of the reservoir Drill-In Fluids were designed with acid soluble weighting agents particularly if it isopen hole or completing with screens. These weighting agents comes in different sizes and needs to idenitify an appropriate size or a combination of particles that can able to just bridge the reservoir without invading the reservoir. This invasion of solid particles along with the filtrate entered into the formation later contributes to skin damage. Ordinary surfactants cannot able to remove this damage to larger extenet and hence specially deisgned surfatant system have been developed to remediate near-wellbore damage caused by drilling and completion fluids. The properties of these treatment systems include their ability to solubilize oil and reduces the interfacial tension (IFT) significantly between the organic and aqueous phases which effectively diffuses through the damaged zone without external energy. The inherent properties of these systems make the it ideal for removing induced formation damage as well as an excellent option for aciding the solid particles invaded and make the reservoir completely water-wet. As the time progress and when the formation gets depleted; many accumulations of fine migrates and heavy hydrocarbons are highly expected around the formation tip that normally results in a reduction of hydrocarbon flow. This problem can be eliminated by squeezing such new surfactant into the formation, easily enhaces the production rate and the flow lost would be restored. In open-hole (OH) completions, this specialized surfactant designs have proven very effective in removing Oil Base Mud (OBM) filter cake damage uniformly with delayed reaction time. In cased-hole (CH) completions, these systems have demonstrated a high degree of efficiency to clean damaged perforations with spontaneous reaction time. This paper presents a technical overview of this relatively new surfactant systems that are suitable to treat for OH and CH remediation operations. The testing methods mentioned in this paper were able to qualify the right type of remediation fluids that can be used for the removal of damage caused before the system is peumped into the well. The main objective of these specialized surfactant systems is to remove the damage caused by OBM filter cakes and improve the production of hydrocarbon instead of drilling a new side track or a well.