Simulation and Experimental Study on Characteristics of Multiorifice Nozzle in Radial Jet Drilling

The radial jet drilling (RJD) is a key technology to improve the development efficiency of low-permeability oil and gas resources. In order to seek a reasonable hydraulic engineering parameter combination of hydraulic radial jet drilling, to obtain the optimal hydraulic energy distribution, a jet radial horizontal drilling simulation experiment system of the casing windowing is designed. A sequence of experimental investigations focused on engineering parameters of pump displacement, rotating speed, and frequency of high-pressure plunger pump is performed, and the operability and the feasibility of the experiment are verified. To evaluate the maximum drillable length and the self-propelled force of a jet nozzle, a 3D numerical model based on ANSYS-CFX is developed to evaluate the effects of the inlet flow displacement, the flow rates ratio K , and the angle ratio F : B of the forward orifice and backward orifice of the jet nozzle on its maximum drillable length and self-propelled force by sensitivity analysis. Finally, the comparison of numerical simulation results (Ln), mathematical results (Lm), and experiment results (Le) of the maximum drillable length are presented. It is observed that the simulation results are consistent with the experiment results with an average accuracy of 97.07%. Therefore, the proposed numerical model has a good performance in predicting the maximum drillable length of the multiorifice nozzle. The research results can provide theoretical guidance for improving the rock breaking and drilling capability of radial jet drilling technology.

Results of the development system optimization and increasing the efficiency of carbonate reserves extraction of the turney stage of the Chetyrmansky deposit

The article is devoted to the issue of optimizing the development system and increasing the efficiency of carbonate deposits of the Tournaisian stage of the Chetyrmanskoye field developing, and the formation of a strategy for their additional development. As a result of the horizontal drilling, the rate of withdrawal from current recoverable reserves in the main area in terms of reserves increased from 0.3 to 5%, which confirms the high efficiency of horizontal wells drilling with multi-stage hydraulic fracturing in reservoirs with high stratification and heterogeneity degree of the productive section in order to increase the rate of reserves production and achieve the approved oil recovery factor, as well as the high efficiency of the proposed methodological approach in the design of the facility development by a system of horizontal wells, the correct choice of the facility development strategy in the design solutions formation. Keywords: oil fields development; carbonate deposits; development of reserves; multi-stage hydraulic fracturing; horizontal well.

Structural Reservoir Characterization of Akkas Gas Field, Western Iraq: Implications for Hydrocarbon Recovery

Akkas Field is a structural trap with a sandstone reservoir that contains proven gas condensate. The field is a faulted anticline that consists of the Ordovician Khabour Formation. The objective of this research is to use structural reservoir characterization for hydrocarbon recovery. The stratigraphic sequence of the Silurian and older strata was subjected to an uplift that developed a gentle NW-SE trending anticline. The uplifting and folding events developed micro-fractures represented by tension cracks. These microfractures, whether they are outer arc or release fractures, are parallel to the hinge line of the anticline and perpendicular to the bedding planes. The brittle sandstone layers of the reservoir are interbedded with ductile units of shale. The sandstone layers accommodate the formation of micro fractures that play a major role to increase the secondary porosity. The gas and condensate have been stored mainly through the micro fractures. Two types of drilling have been used for experimental gas production, vertical and horizontal. Horizontal drilling was parallel to both hinge line of the anticline and micro fracture surfaces that was conducted and doubled the gas production of the vertical well multiple times. However, if used the third type of drilling, directional, that is perpendicular to the hinge line and parallel to the beddings of both flanks of the anticline gas production will increase more than the horizontal drilling. The directional drilling will become perpendicular to the fracture surfaces and allow the gas and the condensate to flow into the well from all directions. Additionally, it will reduce the effect of both semi – liquid hydrocarbon condensate and vertical sediment barriers.

Workflow to Optimize Cluster Spacing Design of Horizontal Multistage Fractured Well in Unconventional Source Rock

Horizontal drilling and multistage hydraulic fracturing applied in unconventional reservoirs over the past decade to create a large fracture surface area to improve the well productivity. The combination of reservoir quality with perforation cluster spacing and fracture staging are keys to successful hydraulic fracturing treatment for horizontal wells. The objective of this work is to build and calibrate a dynamic model by integrating geologic, hydraulic fracture, and reservoir modeling to optimize the number of clusters and other completion parameters for a horizontal well drilled in the source rock reservoir using simulation and analytical models. The methodology adopted in this study covers the integration of geological, petrophysical, and production data analysis to evaluate reservoir and completion qualities and quantify the heterogeneity and the perforation clusters number required within a frac stage. Assuming all perforation clusters are uniformly distributed within a stage. The hydraulic planer fracture attributes assumed and the surface production measurement together with the production profile were used to calibrate the reservoir model. The properties of the Stimulated Reservoir Volume "SRV" were defined after the final calibration using reservoir model including hydraulic fractures. The calibrated reservoir model was used to carry out sensitivity analyses for cluster spacing optimization and other completion parameters considering the surface and reservoir constraints. An optimum cluster spacing was observed based on the Estimated Ultimate Recovery "EUR" of the subject well by reservoir properties. The final results based on 70% of perforation clusters contribution to production observed from PLT log, and the results of this study were implemented. Afterwards, another study has been undertaken to increasing the stimulation effectiveness and maximizing the number of perforation clusters contributing to productivity as an area for improvement to engineering the completion design. The methodology adopted in this study identifies the most important parameters of completion affecting well productivity for specific unconventional reservoirs. This study will help to engineer completion design, improve cluster efficiency, reduce cost and increase well EUR for the development phase.

Unconventional Drilling and Creative Solutions Delivered World Record a Multi-Laterals Fishbone all Legs Drilled, Accessed and Stimulated First Attempt - Case Study from Kuwait

Despite being the first area for oil to be found in Kuwait in mid 1930's, Bahra's oil production remained largely unexploited until 2015, when a major development campaign targeting one of its tight carbonate reservoirs through horizontal drilling and multi-stage frack completions was commissioned. Nonetheless, with the development and exploration initiatives underway, surface congestion is the primary challenge. As the number of wells increased the need for unconventional well profiles became more demanding. The multi-lateral fishbone approach was designed to have a total of four laterals with approximately 3000 ft each. Lessons learned from previous level-1 multi-laterals drilled in North Kuwait indicated that the primary challenge remained to be the ability to drill a smooth bore hole profile across the junctions to successfully re-access and stimulate all the drilled legs with coil-tubing to maximize production. Kuwaiti Operator Reservoir and study team were looking for an alternate solution to increase the production in Bahra using multi-laterals technics in the same reservoir to stimulate and sustain production in calcite reservoir. Historically only three wells were drilled experimenting challenges and failures to open hole sidetrack leading to have long time to complete the wells with maximum 3 legs as record including the mother hole. RST team asked to drill a well with 4 legs, each leg following the same azimuth with the condition to be 300 ft apart. The thorough planning exercise completed and the close follow-up to the approved design of service during execution phase resulted in the successful delivery of the first four legs fishbone in Kuwait with Zero Non-Productive Time. In addition to achieving all the geological targets, the smooth borehole profile helped ensure successful re-entry and stimulation of all four legs in the same run achieving the well challenge using the unique

Efficient Drilling Technology of Horizontal Wells in the Duverney Block in Canada

Recent years, both exploration and development have made considerable progress in the Duverney block shale gas in Canada. However, technical problems exposed in horizontal drilling engineering need to be optimized: 1) Loss is common in shallow formations; 2) High downhole friction torque, low ROP and drilling cuttings accumulation in long horizontal well section; 3) Borehole instability leads to hanger or packer failure; 4) Drill bits and PDM have short servicing life and low efficiency. Optimization comes from three aspects: (1) Based on previous drilling experience and latest formation condition and development requirement, we design a new well profile for the block taking into drilling safety and further development account;(2) Optimize strong inhibitive, easy-maintenance and high cutting-carrying capacity OBM to ensure the safety requirements in the ultra-long open hole section; (3) BHA and parameters optimization. Optimize drill bit with high-abrasiveness and axial efficiency according to logging data, drillability and UCS. Upgrade conventional PDM into high-performance PDM with even-wall thickness. By means of simulation and calculation, drilling parameters suitable for Duverney block has been optimized. Based on the optimization above, a stable and efficient well profile has been improved solving hanger failure on-site efficiently and complete with composite casing design (4-1/2 inch plus 5 inch) in reservoir section; a 90/10 oil-water ratio OBM has been optimized and applied onsite; Combined with high performance PDC bit and even-wall PDM as well as optimized drilling parameters, higher ROP and longer horizontal section have been achieved. The optimization has made successful field application results:(1) Completion depth has been deepened gradually, from 18,080 ft in 2013 to 23,208 ft at present, with an increase of 28.3%;(2) Horizontal section length has been increasing dramatically, from 6,190 ft in 2013 to 10,301 ft at present, with an increase of 66.4%;(3) The average drilling cycle has been shortened, from 51 days in 2013 to 26 days at present, with a decrease of 48.8%;(4) The average ROP has increased steadily, from 71.2ft/h in 2013 to 82.12ft/h at present, with an increase of 15.3%; (5) Drilling costs per meter have been significantly reduced, from 442.4 CAD/ft in 2013 to 228.3 CAD/ft at present. Combining the optimization and matching design above, it has effectively solved the difficulties of the Duverney block drilling engineering and achieved good field application effects: well depth and horizontal section length in the block have been deepened year by year, the drilling cycle and cost have been decreased year by year, as well as the economic effect has been significant. In all, the research achievements provide a practical and effective reference for horizontal wells in other region especially for the unconventional gas.

Applying geological and mathematical modeling to predict fluid influx in horizontal wells (the case of Kalamkas oil field)

One of the ways to increase well oil production is to reduce the filtration resistance of the bottom-hole zone. Along with well-known stimulation methods, such as modern methods of treating wells bottom-hole zone, side tracking (drilling of lateral horizontal boreholes) is of great interest. The following works have been implemented Kalamkas field: a complex of geological, geophysical and field exploration; correlation schemes to track the lithology of the formation; clarifying structural maps and engineering maps; justifying activities to select one or more wells for horizontal drilling; hydrodynamic calculations and estimating their flow rate.

Synchronization and Stability of a Three Co-Rotating Rotor System Coupled with Springs in a Non-Resonance System

With the rapid development of horizontal drilling technology, the drilling fluid shale shaker (DFSS) features high capacity and high efficiency. Hence, a vibrating mechanism of a three co-rotating rotor system coupled with springs is proposed for designing large-sized and heavy-duty vibrating screens in petroleum drilling engineering. To master synchronization of the vibrating system, the dynamic equations of three corotating rotors coupled with springs are first developed based on Lagrange’s equations. Second, synchronous conditions of the system are derived based on the average method, and its stability criterion is obtained by adopting Hamilton’s principle. Furthermore, the influences of various factors, including positional parameters of three motors, stiffness coefficient of the springs and frequency ratio on synchronization behaviour, are numerically analysed in the steady state. Additionally, the Runge–Kutta algorithm with adaptive control is employed to build an electromagnetic coupling model, and the relationships between the synchronization state of the system and its mechanical-electrical coupling characteristics are investigated. Finally, an experimental prototype is designed to validate the theory and numerical analysis. The research result shows that the in-phase synchronization of three co-rotating rotors coupled with springs is easy to implement with the selection of a sufficiently large stiffness.

Study on the Mechanical Extended-Reach Limit Prediction Model of Horizontal Drilling with Dual-Channel Drillpipes

Extended-reach horizontal wells are critical for the development of unconventional reservoirs. Dual-channel drill pipe drilling has a great advantage in improving the horizontal section length, while the research on its mechanical extended-reach limit prediction model is insufficient. In this paper, the torque and drag model is built considering the additional axial force of the sliding piston on the dual-channel drillpipe. Based on the torque and drag model, the mechanical extended-reach limit model for dual-channel drilling is established. A case study including a comparison to the conventional drilling method and sensitivity analysis is conducted. The result shows that under the same conditions, the mechanical extended-reach limit of the dual-channel drilling method is 10,592.2 m, while it is 9030.6 m of the conventional drilling method. The dual-channel drilling method achieves a further mechanical extended-reach limit than the conventional drilling method. To improve the mechanical extended-reach limit of dual-channel drilling, a higher back pressure on the sliding piston, a deeper measured depth of the sliding piston, a higher density of the passive drilling fluid, a smaller outer diameter of the outer pipe, a lower weight on bit and rate of penetration should be adopted. The work in this paper completes the extended-reach limit theory of dual-channel drilling, providing a guide for better use in unconventional reservoir development.