Geothermal formations are hot, often hard, highly fractured and under-pressured. They often contain corrosive fluids and some formation fluids that have very high solids content. These harsh environments mean that drilling is usually difficult. Challenges include degradation of drilling fluids with associated variances in fluids properties, difficulty in managing mud systems, slow rate of penetration, short bit life and lost circulation. The potential for fines migration and induced formation damage in geothermal wells is significantly high due to weakening of attaching electrostatic forces under high temperatures and as a result of thermal contraction. Through case histories, this paper presents drilling challenges and the mechanisms of reservoir damages. The paper will also show the workflow and methodology of using the integrated geosciences analysis in pre-planning to mitigate the challenges related to geothermal activities. Understanding geothermal reservoirs challenges requires a systematic workflow including but not limited to the following: structural geology, mineralogy, geochemistry, drilling fluid chemistry, high-temperature rock-water-fluids interactions, drill bit selection, and geomechanics modeling. ThermoChemo-Poroelasticity stability analysis is also an important consideration. Lab work to properly select the drilling fluids chemicals is required to optimize the drilling fluids parameters and simulating bottom hole temperature. The outcomes from geology, mineralogy, geochemistry and geomechanics will be considered for optimum drilling fluids selection and fluids formulation optimization. The ultimate outcomes include but are not limited to MWT limits (Window), Breakout width, Pmud to trigger slip, drilling fluids formulation effects, drilling bits selection and surface parameters optimization. For reliable performance in high-temperature environments, we need to consider the following: Know your geothermal reservoir; rock type, mineralogy, geochemistry, structural controls, geomechanics and Thermo/Chemo-Poro-elasticity conditions.Matching your injected water chemistry to formation water chemistry is very important, especially in high TDS geothermal brines. Incompatible total dissolved solids (TDS) concentrations will alter the ion carrying capacity, disturb the natural reservoir equilibrium and can lead to formation damage.Optimizing drilling fluid selection.Hydraulics, gel breaking, swab and surge including thermal effects.High-performance drill bits to keep you in the hole longer, reducing trips and saving you moneyAdvanced drilling technologies to deliver fast, efficient wellbore construction, including specially engineered motors for extreme operating environments, automated drilling systems, and high-temperature MWD technologies.

Poor drilling performance can lead to increased costs when enhanced drilling performance and extended reach are the main goals for oil operators. Service companies and operators can use the latest technology and several pre-well planning processes and methods to enhance drilling operations effectively and attain these goals. These processes include developing a thorough understanding and application of the geological structure and conducting a formal planning process that incorporates all aspects of drilling, well design, formation evaluation, bit selection and bottomhole assembly. In this dynamic market where companies are trying to minimize the cost and attain the objective, basic planning and execution using the latest advanced technology are not enough to provide significant performance improvements. Extensive job planning, including sensitivity analysis, is essential. During the execution phase, close monitoring of drilling parameters and continual testing against modeled data help identify hazards early. Enabling quick and informed decisions to ensure safe and efficient drilling in a challenging environment will be one of the main factors to improve performance. Using the right downhole optimization tool with highly experienced engineers enable the interaction with real-time parameters. That's the key factor to overcome extended-reach challenges such as Steering in different environmentsVibrationsTransfer of usable energyHole cleaning and quality indications Supporting downhole optimization with real-time geomechanics will influence the success rate to deliver the expected performance. The involvement of geomechanics in the planning stage and during execution enables faster and safer drilling and resolves many challenges in extend-reach wells such as Wellbore stabilityHole qualityHole cleaningPressure managementTorque and dragMud system and properties This paper highlights the importance of utilizing a downhole optimization tool and real-time geomechanics by describing a case study from the Middle East.

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.

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