Scaling Formulae for the Wellbore Hydraulics Similitude with Drill Pipe Rotation and Eccentricity

Equivalent circulation density of the fluid circulation system in drilling rigs is determined by the frictional pressure losses in the wellbore annulus. Flow loop experiments are commonly used to simulate the annular wellbore hydraulics in the laboratory. However, proper scaling of the experiment design parameters including the drill pipe rotation and eccentricity has been a weak link in the literature. Our study uses the similarity laws and dimensional analysis to obtain a complete set of scaling formulae that would relate the pressure loss gradients of annular flows at the laboratory and wellbore scales while considering the effects of inner pipe rotation and eccentricity. Dimensional analysis is conducted for commonly encountered types of drilling fluid rheology, namely, Newtonian, power-law, and yield power-law. Appropriate dimensionless groups of the involved variables are developed to characterize fluid flow in an eccentric annulus with a rotating inner pipe. Characteristic shear strain rate at the pipe walls is obtained from the characteristic velocity and length scale of the considered annular flow. The relation between lab-scale and wellbore scale variables are obtained by imposing the geometric, kinematic, and dynamic similarities between the laboratory flow loop and wellbore annular flows. The outcomes of the considered scaling scheme is expressed in terms of closed-form formulae that would determine the flow rate and inner pipe rotation speed of the laboratory experiments in terms of the wellbore flow rate and drill pipe rotation speed, as well as other parameters of the problem, in such a way that the resulting Fanning friction factors of the laboratory and wellbore-scale annular flows become identical. Findings suggest that the appropriate value for lab flow rate and pipe rotation speed are linearly related to those of the field condition for all fluid types. The length ratio, density ratio, consistency index ratio, and power index determine the proportionality constant. Attaining complete similarity between the similitude and wellbore-scale annular flow may require the fluid rheology of the lab experiments to be different from the drilling fluid. The expressions of lab flow rate and rotational speed for the yield power-law fluid are identical to those of the power-law fluid case, provided that the yield stress of the lab fluid is constrained to a proper value.

Interdisciplinary Approach for Wellbore Stability During Slimhole Drilling at Volga-Urals Basin Oilfield

The design features and the need to use a water-based solution make the task of ensuring trouble-free drilling of vertical wells non-trivial. This work is an example of an interdisciplinary approach to the analysis of the mechanisms of instability of the wellbore. Instability can be caused by a complex of reasons, in this case, standard geomechanical calculations are not enough to solve the problem. Engineering calculations and laboratory chemical studies are integrated into the process of geomechanical modeling. The recommendations developed in all three areas are interdependent and inseparable from each other. To achieve good results, it is necessary to comply with a set of measures at the same time. The key tasks of the project were: determination of drilling density, tripping the pipe conditions, parameters of the drilling fluid rheology, selection of a system for the best inhibition of clay swelling.

Field Testing of the Flowback Technology for Multistage-Fractured Horizontal Wells: Generalization to Find an Optimum Balance Between Aggressive and Smooth Scenarios

We present the results of field experiments campaign on start-up of wells located in a sandstone oilfield of Western Siberia and history matching of coupled "wellbore-hydraulic fracture" model describing well start-up and fracture clean-up. The conclusion is made about the impact of rheological and geomechanical factors on the well cumulative production andfracture conductivity.The results are generalized for four wells of the field experiment and 30 wells of the retrospective analysis. Calculations of well startup are carried out using standalone fracture cleanup model and the coupled model, which includes models for filtration inside closed hydraulic fracture and flow in the wellbore. The data obtained during field tests on well startup is used to history match the fracture clean-up model. The adaptation allows to evaluate the sensitivity of well production to various physical parameters and find the safe operating envelope of operational parameters during well startup. Numerical simulations allow take into account geomechanics effectsand rheology properties of fracturing fluid, study the dynamics of effective (cleaned) fracture length as well as evaluate the influence of pressure drop dynamics on filtration properties of the fracture and cumulative well production. We extended the number of wells to study the impact of flowback scenarios on production andgeneralized the results of our previous study.Key parameters affecting the history match process of the mathematical model are determined,the uncertainty associated with fluid rheology is reduced. Using the history-matched model, we evaluated geomechanics effects on fracture degradation depending on bottom-hole pressure drop dynamics. Based on the obtained dynamics of dimensionless parameters, such as pressure and fracture productivity, we propose an optimized well start-up strategy aimed at maximizing effective fracture length and cumulative production. Additionally, we visualized the dynamics of fracture conductivity distribution along its length. The obtained results are consistent with interpretation of physical processes accompanying well start-up and fracture clean-up. Dimensionless productivity index is chosen to quantify the effects of geomechanics and fluid rheology on well production.On the basis of matched mathematical model, we predict a potential increase in production of the well with optimized start-up.The recommendations are presented in the form of the dynamics of wellhead choke opening and a sequence of choke diameters. We propose an integrated approach for planning a well flowback strategy after multi-stage hydraulic fracturing. The proposed decision-making algorithm considers the effects of geomechanics and yield-stress hydraulic fracturing fluid rheology on cumulative production. It allows to develop a design for the well start-up and fracture cleanup in terms of dynamics of wellheadchoke opening.

Remote Reservoir Exploration in Odoptu-More Field by Delivering ERD Wells Using Multilateral Drilling Technology

This paper provides the results that were achieved and shares the drilling unique practices that were implemented to deliver the first complex bilateral extended reach drilling (ERD) well in Odoptu-more field (North Dome). Well design driven by geological objectives considered drilling 215.9mm main and pilot holes (PH). Well complexity was governed by the type of a profile having ERD ratio of 5.22 (main hole) / 4.60 (PH) and trajectory's 3D nature (turn in azimuth of 90 degrees) compared to previous wells in the project drilled mainly with 2D profiles. Apart from the problems connected with drilling and casing upper sections key challenges comprised kicking off in 215.9mm open hole at 5955m MD and 1512m TVD with rotary steerable system, setting cement plugs at shallow true vertical depth (TVD) at 89 degrees of inclination to abandon laterally drilled PH, delivering 168.3mm production liner to bottom with a risk of entering a lateral while running in hole. An effective collaboration between integrated engineering team and customer departments went far beyond ERD standard set of operations already existing in the project thus allowing to break its own records and to set new achievements due to integrated technological approach. The longest 444.5mm section (2975 m) was drilled in one run achieving the record daily drilling rate and rate of penetration (ROP). Cementing of 244.5mm floated liner resulted in the highest good cement bond integrity percentage ever achieved among other wells in project due to new ways of casing standoff and fluid rheology hierarchy modeling. For the first time in the project 215.9mm main horizontal hole in extreme reach ERD well has been drilled by kicking off in open hole from the pilot horizontal one with push-the-bit rotary steerable system without a kickoff plug with pilot hole being abandoned by setting cement plugs. Project-specific risk assessment conducted by team allowed successful deployment of 168.3mm liner into the main hole. Moreover, due to thorough engineering planning electrical submersible pump (ESP) was run without extending 244.5mm liner to surface by tie-back thus saving additional 7 days. Drilling first bilateral ERD well unlocked opportunities for the operator to reach, explore and develop different extended geological targets thus eliminating well construction process of additional wells on drilling upper sections.

Proppant Transport Using High-Viscosity Friction Reducer Fracture Fluids at High-Temperature Environment

Summary The stimulation of unconventional reservoirs to improve oil productivity in tight formations of shale basins is a key objective in hydraulic fracturing treatments. Such stimulation can be made by reliable fracture fluids that have a high viscosity and elasticity to suspend the proppant in the fracture networks. Recently, due to several operational and economic reasons, the oil industry began using high-viscosity friction reducers (HVFRs) as direct replacements for linear and crosslinked gels. However, some issues can limit the capability of HVFRs to provide effective sand transport, including the high fluid temperature during fracture treatment inside the formations. This may lead to unstable fracture fluids caused by a decrease in the interconnective strength between the fluid chains, which results in reduced viscosity and elasticity. This study comprehensively investigated HVFRs in comparison with guar at various temperatures. An HVFR at 4 gallons per thousand gallons of water (gpt) and guar at 25 pounds per thousand gallons of water (ppt) were selected based on fluid rheology tests and hydraulic fracture execution field results. The rheological measurements of both fracture fluids were conducted at different temperature values (i.e., 25, 50, 75, and 100°C). Static and dynamic proppant settling tests were also conducted at the same temperatures. The results showed that the HVFR provided better proppant transport capability than the guar. The HVFR had better thermal stability than guar, but its viscosity and elasticity decreased significantly when the temperature exceeded 75°C. An HVFR can carry and hold the proppant more deeply inside the fracture than liner gel, but that ability decreases as the temperature increases. Therefore, using conditions that mimic field conditions to measure the fracture fluid rheology, proppant static settling velocity, and proppant dune development under a high temperature is crucial for enhancing the fracture treatment results.

An optimization-based design approach for a novel self-adjuster using shear thickening fluid

Recently, the increasingly strict safety and emission regulations in the automotive industry drove the interest towards automatic length compensating devices, e.g., hydraulic lash adjusters (lower emission) and slack adjuster in brake systems (faster brake response). These devices have two crucial requirements: (a) be stiff during high load, while (b) be flexible in the released state to compensate for environmental effects such as wear and temperature difference. This study aims to use the advantageous properties of shear thickening fluids to develop a less complicated, cost-efficient design. The proposed design is modeled by a system of ordinary differential equations in which the effect of the non-Newtonian fluid flow is taken into account with a novel, simplified, semi-analytical flow rate-pressure drop relationship suitable for handling arbitrary rheology. The adjuster’s dimensions are determined with a multi-objective genetic algorithm based on the coupled solid-fluid mechanical model for six different shear thickening rheologies. The accuracy of the simplified flow model is verified by means of steady-state and transient CFD simulations for the optimal candidates. We have found that the dominating parameters of such devices are (a) the shear thickening region of the fluid rheology and (b) the gap sizes, while the piston diameters and the zero viscosity or the critical shear rate of the fluid have less effect. Based on the results, we give guidelines to design similar-length compensating devices.

Implication of fluid rheology on the Cattaneo–Christov heat flux theory for fourth grade nanofluid over a riga device with thermal radiation

This paper analyzes the influence of mixed convective fourth grade nanofluid flow by a stretchable Riga device in the presence variable thermal conductivity and mass diffusivity. Heat and mass transportation are considered with Cattaneo–Christov (CC) model. Thermal radiation and dissipation are also taken in the energy expression. Suitable transformation is employed to reduce partial differential system into nonlinear ordinary system. The governing nonlinear expression is solved via optimal homotopy analysis method. Impact of different physical variables is discussed via graphs. Velocity profile is enhanced for higher values of cross viscous parameter and fourth grade fluid variable. Fluid temperature enhances for higher estimation of thermal relaxation parameter but reverse behavior is seen for solutal concentration variable on nanoparticle concentration.

Chelating Agents Usage in Optimization of Fracturing Fluid Rheology Prepared from Seawater

Hydraulic fracturing consumes massive volumes of freshwater that is usually scarce and costly. Such operation is not sustainable, and hence seawater could be used as an alternative. Nevertheless, seawater has high total dissolved solids (TDS), affecting the fracturing fluid rheology and providing a damage potential to the subterranean hydrocarbon reservoirs. Resolving these issues requires fracturing fluid systems with many additives, which results in an expensive and non-eco-friendly system. This study proposes eco-friendly and biodegradable chelating agents that could replace many additives such as scale inhibitors and crosslinkers. The study aims to optimize the rheology of seawater fracturing fluids using a chelating agent and polymer. By optimizing N,N-Dicarboxymethyl glutamic acid (GLDA) conditions, high viscosity was achieved using a standard industry rheometer. The GLDA was mixed with carboxymethyl hydroxypropyl guar (CMHPG) polymer and tested in both deionized water (DW) and seawater (SW). The polymer was examined first, where the rheology did not show a time-dependent behavior. The polymer in SW showed a slightly higher viscosity than in DW. The GLDA and CMHPG were tested at different temperatures, pH, and concentrations. These sets showed a time-dependent viscosity behavior, which can be utilized in various fracturing steps. Results showed that the solution pH and GLDA concentration significantly impacted the fluid viscosity magnitude and behavior. The developed formulation is shear thinning, where the viscosity declines as the shear rate increases. The temperature negatively impacted the viscosity and caused the formulation to break. The study provided an understanding of how to optimize the rheology of SW fracturing fluid based on GLDA chelating and CMHPG polymer.