Accurate wellbore hydraulics simulations have been effective in assisting engineers to budget well time and materials, design and execute safe, optimum drilling operations. In this context, "accurate" is commonly understood as 0.1 pound per gallon (ppg) delta, or less, between measured and predicted equivalent circulating density (ECD). Extended-reach-drilling (ERD) wells have been gaining recent adoption due to advancements in drilling technologies. This type of well, by its geometrical nature, poses a challenge to pressure management, hole cleaning and wellbore stability. This increases the relevance of simulation aids. Simultaneously, the industry has seen challenges in achieving the accuracy levels required to model and simulate these wells appropriately. This work closes this gap. Several factors affect the accuracy of ECD predicting algorithms, including but not limited to: the wellbore geometry, pumping schedule, formation and fluid's temperature profiles, physical properties and drilling parameters. Offset information from five different wells was used as basis of investigation and verification. While opportunities for better simulation set-ups were found, it was also identified that refinements to the modeling assumptions were required. The prediction for these wells was enhanced by taking an existing drilling simulator and (1) improving the accuracy of pipe positioning estimation; (2) augmenting the understanding of the eccentric annular flow-field; and (3) including the effects of pipe rotation. This led to a superior determination of the downhole flow-regimes, pressure drops, cuttings transport efficiencies and constrictions due to cuttings beds accumulation. The presented enhanced simulator has been validated against 10+ additional wells. The prediction accuracy significantly improved where it previously lacked. Simultaneously, accuracy was maintained (or slightly improved) in conditions where it originally performed. For ERD wells as shallow as 5,000ft TVD and MD's in excess of 40,000ft, the original ECD predictions diverged as much as 1.5ppg (~400psi) from pressure-while-drilling (PWD). The achieved superior predictions were never above 0.1ppg (~26psi) delta when compared to PWD. Using this advanced simulator, engineers were able to tailor the appropriate rheology profiles to drill ERD wells at optimum performance and determine the best fluid systems’ configuration to achieve it. Operations were completed as planned and budgeted, without unexpected changes in drilling parameters This work presents an enhanced methodology to accurately model annular pressure drops in ERD wells. In addition to accounting for the appropriate flow-regime transitions in a downhole eccentric annulus, this method provides a "true north" as far as "tolerable" cuttings bed accumulation to maintain pressures within formation limits. By using this simulator, engineers were able to customize drilling fluids rheology profiles for minimum pressure loss gradients at performant sag resistant levels, and safely drill challenging ERD wells.

Drilling operational parameters, such as pump rate, pipe tripping speed, and drilling fluid time-dependent rheological characteristics can impact wellbore pressure management and equivalent circulating density (ECD). It is important that ECD at any instant remain between fracture and pore pressure gradients (drilling window). This paper presents modeling ECD for transient wellbore conditions, which demonstrates the model predictions match pressure while drilling (PWD) measurements obtained from several wells. Drilling fluids exhibit time-dependent rheological response particularly at static or low-shear conditions. The fluids develop gel microstructure attributed to interaction between polymers, colloidal particles, and emulsion droplets. As pumping is initiated or pipe moved, ECD spikes occur because of the developed gel microstructure; then, the microstructure breaks down gradually with shearing. Understanding the mechanism of gel formation and breakdown under various shear, temperature, and pressure conditions improves accuracy of the ECD modeling for transient fluid characteristics. Pump rate can accelerate or decelerate during several operations (e.g., during pipe connections). Another operational parameter, tripping speed, can exhibit variation. For example, pipe speed can accelerate from static to the highest speed; then, decelerate to static. Furthermore, the fluid can be pumped during tripping operations to help manage wellbore pressure. In addition, such pumping helps speed up tripping; thus, saving rig time. The coupled effect of momentum change during these transient operational parameters in addition to time-dependent fluid properties on ECD response is investigated, exhibiting improved understanding of transient effects improves ECD modeling accuracy for such conditions. The developed models for ECD response were validated on several wells. Fluid properties, real-time pump rate, and tripping speed information were used as model inputs, while outputs were compared with PWD data obtained from the wells. With successful validation, these models can now be used for improved design of operational parameters and fluid characteristics for wellbore management.

Uncertainties in the drilling process result in safety factors or safety margins sufficient to minimize risks in the drilling process. These safety margins represent inefficiencies in the system. This paper will discuss a method for reducing uncertainty as it relates to well bore pressures and hole cleaning to eliminate or reduce these inefficiencies, quantify the rates of penetration that can be achieved, and illustrate the expected wellbore pressures generated by these rates of penetration. When data is collected manually, the nuances of fluid changes are lost between property measurements. This paper will illustrate the difference between calculating equivalent circulating densities (ECD) with manually collected mud report data and fluid properties collected in real time and the impact that this can have on optimizing the rate at which the operator can drill and trip pipe. A patent-based methodology will be presented, in which real-time drilling and fluids data are captured and utilized to model ECD pressure data related to the bore hole. The actual and modeled data are statistically analysed to infer information about how rapid a rate of penetration (ROP) may safely be employed to optimize drilling results. Data will be presented demonstrating the impact that small improvements in fluid parameters and drilling operations can have over the course of drilling a well. The role that a real-time hydraulics software model plays in providing predictive analytics for ROP optimization will also be discussed. Predictive analytics enable operators to look several stands ahead of the bit to determine if the ROP drilled will cause issues in the future. This enables the identification of the maximum ROP that can be drilled versus optimizing instantaneous ROP. This enables operators to optimize casing-to-casing time.

Replicating downhole conditions using real-time software helps reduce nonproductive time. Hydraulic outputs trend against sensor outputs, enabling event detection. Using real-time fluid properties with fluid tracking hydraulic software helps improve predictions for comparison, enabling faster and more reliable detection of downhole conditions. Two instances of real-time hydraulics simulators capable of tracking property changes of fluid and the positions of discrete fluid volumes within the wellbore were used. One simulator was used with a real-time fluid properties apparatus that provided full six-speed rheology and fluid density in real time. The second simulator used fluid updates provided by the mud engineer on location. The calculated equivalent circulating density (ECD) and predicted standpipe pressure (SPP) from the hydraulics software was compared to actual pressure while drilling (PWD) and measured SPP sensor outputs. The real-time fluid apparatus provided real-time rheology and density values consistently while drilling the section, and data was provided directly to the hydraulics simulator. Comparing ECD predictions with and without the real-time fluid properties made it possible to identify any improvements achieved using such equipment. Although both sets of data showed that the hydraulics simulator was highly accurate, using real-time fluid inputs enabled ECD predictions to trend considerably closer to the PWD measurements. The capability of tracking the predicted ECD against actual sensor outputs enables users to quickly determine deviations in sensor outputs associated with downhole conditions and to observe deviations occurring as a result of inconsistencies within the fluid system. Data presented in this paper are taken from some of the first global deployments of real-time fluid properties measurement equipment used in conjunction with real-time hydraulics software.