bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of Low-Frequency Downhole Electrical Measurements for Mapping Proppant Distribution in Hydraulic Fractures in Casedhole Wells
Authors: Zhang Peng , Sen Mrinal K. , Sharma Mukul M. , Gabelmann Jeff , Glowka David
Published: October 2018

A tool concept using downhole electrical measurements for mapping electrically conductive proppant in hydraulic fractures is presented in this paper. The method relies on direct excitation of the casing, which is expected to overcome the severe limitations of induction tools in casedhole wells. An array of insulating gaps is installed and cemented in place as a permanent part of the casing string. The envisioned electrical measurements are performed by imposing a voltage across each insulating gap, one at a time, before and after hydraulic-fracture operations. The voltages across other insulating gaps near the transmitter gap are recorded.

The proposed tool's response to the geometry of a single fracture was modeled by solving for the electrical potential with a finite-volume method. Previous simulation results have shown that the electrically conductive proppant alters the path of the electrical current in the formation, and this is recorded as differential signals by the string of insulating gaps surrounding the source gap. The simulated differential signals are highly sensitive to a fracture's location, length, and orientation, and less sensitive to the fracture's aspect ratio. However, to enable the implementation of such a practical system, various aspects of the tool concept must be investigated further through simulations. Following our previous work, this paper focuses on the forward modeling of the tool's response to multiple fractures, which demonstrates the influence of these fractures on the signals, and provides important guidance for inverse modeling. Parametric inversion of fractures from synthetic data, generated by exciting various insulating gaps, is solved with very fast simulated annealing (VFSA).

Simulation results show that, when multiple hydraulic fractures are present, the voltages measured at the receiver gaps are determined primarily by the fracture that is in direct contact with the excited section of casing. When two fractures touch the same casing section, they induce voltages very similar to those from a single fracture with the same conductivity and volume. Preliminary inversion results that use synthetic data computed from circular fractures indicate that the proposed VFSA can solve for the multiple fractures’ widths and radii at the same time, without requiring numerous forward simulations. Even with noisy synthetic data, VFSA can make good estimates of the fractures’ parameters. This indicates that the VFSA technique is a proper and robust inversion technique for the measured voltages at various receiver gaps.
Modeling Transient Inflow Performance Relationship in Artificial-Lift Systems
Authors: Xiang Z.. , Kabir C. S.
Published: October 2018

This study presents a transient inflow-performance relationship (IPR) model using the steady-state solution to the diffusivity equation on a periodic varying well-flowing pressure. A wellbore model can be coupled to accurately depict the deliverability from wells with an artificial-lift system (ALS), such as gas lift and plunger lift. The commercial simulators allowed verification of model results and field data validated the solution approach.

For verification of this simplified IPR modeling approach, we first attempted to replicate two-step rate flow and shut-in periods, such as those associated with a transient flow test. Our model successfully reproduced those transient pressure profiles obtained from a rigorous superposition approach, generated with an analytical model using a commercial software package. Thereafter, we replicated the results of a coupled wellbore/reservoir model for a gas-lift well, using a numerical simulator. The difference between the results of rigorous simulators and our simplified transient-IPR model turned out to be well within engineering accuracy.

Field data from two plunger lift operations validated the transient-IPR model presented in this study. One important aspect to note is that a smaller period of oscillation translates into a more significant error between the traditional steady-state IPR model and the actual transient-IPR model. This finding suggested the need for the accuracy of the transient-IPR model in ALS to express the realistic rates and pressures. By capturing the essence of transient behavior, it is possible to combat downhole tool failures due to large pressure fluctuations or issues with surface metering due to higher than expected rates.
Surfactant Batch Treatment Efficiency as an Artificial Lift Method for Horizontal Gas Wells
Authors: Gcali Cikida , Karami Hamidreza , Pereyra Eduardo , Sarica Cem
Published: October 2018

Liquid accumulation in deviated gas wells is a major challenge in production systems. Limitations with the use of gas lift, pumping or plunger lift methods add to this challenge. Recently, surfactants have been injected continuously or as batch to help with the well deliquification by foam generation. The batch treatment is done by intermittent application of soap sticks or liquid surfactants.

This study is an effort to characterize surfactant batch treatment as an artificial lift method in horizontal gas wells. Given the practical potential and yet limited number of studies on this topic, the results can provide an experimental source to optimize surfactant application in mature production systems.

The experimental study is performed in a 2-in ID facility consisting of a 64-ft lateral section with 1° downward inclination followed by a 41-ft vertical section. Water and compressed air are the liquid and gas phases, and an anionic surfactant is applied in batches at the heel of the well. First, static tests are conducted to analyze surfactant efficiency in well start-up conditions. The surfactant concentration, initial liquid loading level and gas rate are varied, and the final liquid loading volume is measured as the target parameter. Then, dynamic tests are conducted to mimic the flowing well conditions. Surfactant concentration, liquid and gas flow rates are varied, and pressure fluctuations at the toe are monitored with time. The surfactant batch is delivered after air-water flow stabilization to investigate the surfactant efficiency. In addition, a high speed camera is used to record the flow conditions.

For well startup conditions, surfactant batch treatment is most effective for lower gas flow rates. Furthermore, the efficacy of surfactants is more pronounced at lesser-loaded wells. The effect of increasing surfactant concentration is eminent below the critical micelle concentration (CMC) with no further improvement beyond CMC. Generally, surfactant batch treatment does not significantly improve well cleanup time.

During well production, surfactant batch treatment is most efficient in low liquid and gas flow rate systems. At increased liquid and gas flow rates, with increasing surfactant concentration, its use can be inefficient due to adverse effects caused by foam frictional pressure losses. When the surfactant batch treatment is efficient, its effect increases with increasing concentration until CMC is reached. During severe slugging, surfactant batch treatment eliminates the slug production phase and partially or fully eradicates the severe slugging depending on the severity of the slugs. Generally, no significant trends can be observed between the period of effectiveness and concentration of surfactant.
Visualizing Rod Design and Analysis Through the Wave Equation
Authors: Phillips Walter
Published: October 2018

Rodstring dynamics are complex and difficult to understand. This work presents a multi-dimensional, interactive visual depiction of the full and intermediate wave equation results for rod design and analysis. Because rod motion exists in both time and space, one can build detailed virtual representations through a series of snapshots on different dimensions. Traditional dynamometer cards are an example of visualizing complex data, through time, in a 2-dimensional context. Extending this into 3-dimensions results in a virtual object generated through time (i.e. a single stroke) and depth (i.e. the rod-string). These visuals can expose a deeper understanding wave dynamics as they travel through the entire length of the rod-string. Further dimensions can be represented by coloring the rendered surface. There are a multitude of such views that can be constructed, all of which stem from the basic 2-dimensional dynamometer cards and time plots familiar to rod pump analysis.
Chamber Gas Lift in Horizontals
Authors: Hardegree C. N. , Gerrard B. A. , Wildman S. L. , McKenzie K. S.
Published: October 2018

This paper highlights a pilot project in which chamber gas lift was installed in two unconventional horizontal wells. Chamber gas lift, as a combination of deep gas lift and intermittent gas lift, allows for an efficient, closed completion with cyclic injection of high-pressure gas, which expands and rapidly displaces fluid at high velocity from deep in the well. Development of the system was a collaboration internally and in conjunction with the vendor to install what was historically a vertical well assembly through the curve section and into a horizontal wellbore. The chamber assembly was successfully designed, sourced, manufactured, installed, and operated. To modify the design from vertical to horizontal applications, components were custom-designed to maintain a sealed chamber. Components deemed most likely to fail are replaceable by slickline intervention. Results indicate a sustained lower downhole pressure than the previous intermittent gas lift system, an increase in production, and good chamber-sweep efficiency.
Energy Management Applied to Electric Submersible Pumping ESP
Authors: Martinez E.. , Caicedo A.. , Paredes L.. , Guevara M.. , Álvarez E..
Published: October 2018

The continuous evaluation of electric submersible pumps (ESP) performance and its integration within the energy management system in the operation of Blocks 16 & 67 of Ecuador allowed to develop a specific procedure to assess the efficiency of ESPs in order to identify energy improvement opportunities.

This procedure is summarized with the Significance Matrix, a tool that integrates ESP's field data such as production history and electrical measurements to estimate hydraulic and electrical power requirements, and a specific method for efficiency evaluation.

The result of the Significance Matrix is the categorization of each ESP system as significant or no-significant use of energy. The significant uses of energy are further analyzed to design an action plan that is prioritized through technical and economic assessment.

The comparison between the Significance Matrix of December 2014 and November 2017 showed that the optimization of eight (8) ESP systems resulted in an average reduction of 49 BDPD in fuel consumption that can be translated to a decrease in greenhouse gases emission of 20 tCO2 per day. Moreover, the increase in average efficiency of the ESP systems from 25.4% to 40.9% projected a reduction of 0.99 MW-day of energy consumption for artificial lift.

This analysis also led to identify wells that were not profitable at the actual operating conditions. A total of 10 wells were closed in the same time period to be replaced with production of more efficient and cost-effective wells.

This approach of energy management was developed considering the methodology of the ISO 50001 standard. The conclusion of the study demonstrated that well intervention to improve energy efficiency of ESP systems led to achieve net cost savings and greenhouse gases emissions reduction.
Material Overview for Electric Submersible Pumps: Part I – Metallic and Ceramic Materials
Authors: Xiao J J , Lastra Rafael , Roth Brian , Lee Woon
Published: October 2018

Electric Submersible Pump (ESP) is a key artificial lift technology to the petroleum industry. Worldwide installations of ESPs are in the range of 130,000 units, contributing to about 60% of the total worldwide oil production. An ESP is made up of hundreds of components integrated together to perform the lifting function. Materials in these components belong to several categories including metals, ceramics, polymers, and others. A good understanding of these materials and vigilant selection for a specific application are critical to the reliability and run life of an ESP system. This paper presents an overview of two classes of materials used in ESP systems: metallic and ceramic materials. A subsequent paper is planned to cover all other categories of materials. The intent is to provide a reference for ESP field application engineers who are responsible for ESP design, component selection, equipment longevity and production optimization.

The information compiled in this paper is a result of extensive literature review. It covers materials used in the motor, protector, pump, and cable (Sensor, packer, Y-tool, diverter valve, surface components of variable speed drives and transformer not included). For each class of materials, it identifies relevant material properties and discusses suitable application conditions.
Efficiency Study in Vizcacheras Field and Implementation of PMM Motors to Increase Production Capability
Authors: Tiofiolo A. L. , Dotta J. J. , Teves R..
Published: October 2018

Vizcacheras is a mature oil field with the highest electric energy consumption among YPF fields. This consumption and the limitations in electrical infrastructure have constrained the growth on the number of ESP lifted wells and consequently the increase of production from the field. Permament magnent motor (PMM) technology was indentified as alternative to reduce power consumption in ESP operated wells in Vizcacheras field. This paper summarizes the field trial of PMM in Vizcacheras field.

The methodology of evaluation includes the power losses calculation of each component of ESP system and the use of hydraulic power as means to make a fair comparison between asynchronous motors (ASM) and PMM. The results of the test shows a total power saving about 17% with a significant reduction of current across ESP power cable and lower motor operating temperature.

Gross estimation about the impact of PMM technology on field and country bases are carried out to show the potential value of this technology in order to increase production by making available energy for other projects and making economically viable those wells with marginal production.
Successful Application of an Innovative Geometry of Progressing Cavity Pump in Application with High Sand and Gas Content. Colombian Successful Case in La Cira Infantas
Authors: Labrador Laura , de Sales Paola , Valderrama Luisa , Molina Jesus , Ferrer Jose
Published: October 2018

Located in the Middle Magdalena River Valley basin, in the department of Santander, municipality of Barrancabermeja in the rural area of El Centro. La Cira-Infantas is the oldest Field in Colombia and with it, the oil industry was born in Colombia. It has proven reserves of 172 MMBOPD, it reached a production of 65000 barrels in 1939 until it declined to 5000 BOPD in 2005. Through an association contract between two operators, looking for the implementation of new technology, in 2017 45000 BOPD were obtained.

During its operation and through the implementation of the secondary recovery method in the field, a high gas and sand content was identified as a problem for high fluid production wells. This has generated premature flailures in the artificial lifting system with Progressing Cavity Pumps during the production of the Arenas C interest zone that raises the costs to the point that makes them economically nonviable. According to the needs of the field and looking for new and better solutions, the design and application of a pump with a special geometry that allowed giving viability to the operation of these problem wells, was performed, thus expanding their run life and reducing costs associated to their intervention. The implementation of this type of pump has allowed a 63% reduction in installation, maintenance and operation costs, and 86% in differed and production loss costs; in general, a 67% economic benefit versus the conventional system was obtained providing technical and economic viability to the development of these reserves.
Innovative Well Designs for HGOR: Extending Gas Production with Common Gas Well Deliquification Techniques
Authors: Goldney J. Clifton , Mohando B.. , Cometto G. Perez , Ballarini M.. , Mazzola R..
Published: October 2018

A novel and flexible completion design for HGOR Wells is presented to cover all the gas well production stages in order to avoid rig interventions during natural flow which would reduce gas production potential due to water influx into the reservoir.

The objective of this paper is to introduce the proposed completion designs so other engineers can apply and improve them in their HGOR wells, maximizing gas production and reducing costs.

After studying the conversions from natural flowing wells to Artificial Lifted wells in which gas production was never recovered, the behavior was determined to be from damage (water blockage) in the near wellbore caused by the fluids used in the rig operations.

A decision was made to anticipate the inherent problems through a flexible completion design that allows for the production of different reservoirs, with tubing and/or annular flow, plunger lift, gas lift, and changing to Sucker Rod Pumping without moving tubing or killing the well, especially in the gas reservoirs.

The flexible completions also allowed for further studies of the well and proposed interventions to assist the flow.
Effective Secondary Recovery Stimulation Using Solid Propellant Technology for Tight Sand Development in Sirikit Oil Field, Thailand
Authors: Toempromraj Wararit , Weeramethachai Deephrom , Kiatrabile Thanita , Sangvaree Thakerngchai , Nadoon Apiwat , Sompopsart Suwin , Duncan Robert , Mai-Cao Lan , Havalda Richard , Havalda Paul
Published: October 2018

The Sirikit Field, a mature onshore field operated by PTTEP in northern Thailand, derives production from sandstone reservoirs. While production from many of the shallow pays have been well-developed and optimized, comparatively few of the deeper and tighter sands have been similarly produced. Various methodologies have been trialed to enhance production from these tight sands and an examination of results will be presented in the context of geology, engineering and economics. This field, like most in the world, was produced initially by primary recovery (natural flow and various artificial lift mechanisms). Later in the development phase, secondary recovery (waterflooding) was implemented in the Sirikit Main area with the aim of improving production from the shallower, higher permeability, reservoirs. The deeper, lower permeability, sands have not undergone secondary recovery. It is foreseen that the vast majority of STOIIP can be extracted from these tight sands and will ultimately be the future of Sirikit long term production.

Several secondary recovery methods were evaluated. Waterflooding was ruled out as an option due to poor reservoir properties which were not favorable for flooding displacement as well as a high injection pressure requirement. The focus then became well stimulation as the main strategy to enhance production from these tight reservoirs. Initial well stimulation technology was the use of larger size perforation guns for the low porosity sands in order to improve reservoir penetration and overcome damage zones. Analysis after field trials showed that the deep penetration perforations had insignificant production improvement. Consequently, solid-propellant technology, which is capable of creating near wellbore fractures, was field trialed. Two types of solid-propellant were tested: "regressive" burning propellant and "progressive" burning propellant. The "regressive" burning propellant results were inconclusive; however, the "progressive" burning propellant results showed clear improvements in production. Moreover, in order to create deeper fractures, "hydraulic fracturing", which requires higher investment, was tested in parallel to the smaller scale investment perforation guns and solid-propellant; however, the results were no better than the "progressive" burning propellant. Consequently, the "progressive" burning propellant provided the positive results at the best economics.

Different well stimulation technologies may be appropriate for varying geologic, engineering and economic conditions. For tight or damaged reservoirs, progressively burning propellant may prove to be the most efficient and cost effective technology for secondary recovery.
Integrated Solution to Optimize Drilling Efficiency and Production in Marginal Tight Oil Field Development: A Case from Songliao Basin, North China
Authors: Wang Wei , Zhao Yuwu , Xue Huizhi , Wang Huijun , Chen Jing , Wang Fei , Fu Zairong , Li Cang , Chen Chengqian , Wang Shuai , Yuan Xiangwei
Published: October 2018

Tight oil filed A located in Songliao Basin North China has been producing for over 15 years. During Phase I, most of primary production came from vertical/directional wells with fracturing operation, the average production is 0.3 ton per well at the end of 2012 and only 8.78% oil recovery is recorded. This marginal oilfield stepped in to Phase II with a horizontal drilling campaign to increase final recovery rate.

The length of planned horizontal section more than 1500m for single well within extra thin tight reservoir (around 1.5m TST). Meanwhile, the budget is very limited during down turn. The drilling efficiency is the most crucial element to ensure the success for this project. Servals challenges was identified during pre-drilling assessment:

Dogleg severity(DLS) in this extra thin laminated reservoir is very unstable base on previous drilling practices Ensure smoothly trajectory control within such narrow geosteering window with high rate of penetrate(ROP)

To overcome above challenges, an integrated solution was developed implemented to this drilling campaign:

Fit for purpose rotary steering system (RSS) was tested including the point-the-bit RSS and push-the bit in this project and found the best solution to ensure efficiency DLS finally. A boundary mapper LWD tool with ability to map multiple key boundaries, this method not only support proactive geosteering to keep trajectory within narrow geosteering window and avoid unnecessary adjustment, out of target or sidetrack, but also can help to keep the trajectory within fast ROP zone during real-time operation.

Two typical wells were completed successfully. Outstanding outcomes have been observed by implementing this integrated approach in the complex target reservoirs. The drilling efficiency was improved by 38.7%~132.6% with smoothly trajectory control. The complex structure was identified clearly and the average Net to Gross (NTG) more that 97.5%, and the production reached to 18ton/day which far exceeding expectation.

The successfully application of the integrated solution in extra thin reservoir tight oil field will lead to improve drilling efficiency and save budget, increasing the production and well economics. We believe this approach and technique could address another similar formation development.
Experimental Study of Frictional Pressure Loss for Eccentric Drillpipe in Horizontal Wells
Authors: Khatibi Milad , Wiktorski Ekaterina , Sui Dan , Time Rune Wiggo
Published: October 2018

The downhole friction is a response to mechanical and hydraulic forces. The mechanical friction takes place when the drillpipe is moving in the wellbore, either in translational or rotational mode. The hydraulic friction occurs due to the circulation of fluids flowing downwards in the pipe, and upwards in the annulus. The additional factors that affect the hydraulic friction are drillpipe rotation, surface roughness, wellbore geometry, etc.

This paper experimentally examines hydraulic friction and studies its variations with adjustable operational parameters (flow rate and rotational speed). The experiments were performed using two pipes, where one was located inside the other. The outside pipe with an inner diameter of 0.04 m simulated the wellbore walls, and the inside one simulated the drillpipe with an outer diameter of 0.025 m. The pipes’ inclination was 5° from the horizontal axis. The drillpipe could be rotated by an electric motor with speeds up to 1000 RPM (revolutions per minute). Spherical glass beads were used to simulate the cuttings behaviour in the wellbore. The pressure gradient variations associated with fluid flow, pipe rotation as well as particles movement was measured over the test section (length of 1.52 m), using a pressure transducer. In addition, a high-speed camera, installed outside the outer pipe, was used to take images of the particles distribution and pipe dynamic oscillations.

The combined effect of fluid flow rate, drillpipe rotation and presence of particles on the hydraulic friction between the outer and inner pipes is investigated in this study. The data analysis for the single-phase liquid flow showed that the pressure loss increased with RPM. It was seen that the secondary flow, created by the drillpipe rotation, was not the only reason to affect the pressure loss, but the drillpipe's eccentricity variations with RPM and flow rate also had a considerable effect. A higher drillpipe eccentricity provided lower friction factor, in the case single-phase liquid flow. Finally, empirical relations to describe the drillpipe eccentricity and hydraulic friction factor as functions of RPM and flow rate were proposed. When the particles were present, the friction factor decreased with RPM.

The above-mentioned conclusions and relations are valid for a Newtonian fluid in the turbulent regime.
Drilling Optimisation in Hard and Abrasive Basement Rock Using a Conical Diamond Element Bit
Authors: Abdila Sayid Faisal , Sondang Jaka , Maaruf Pranefo , Mardiana M. R. , Noviasta Bonar , Astasari Kanya , Febriarto Hendriyan
Published: October 2018

Pertamina EP recently executed an exploration drilling project in Sumatera area. The objective was to evaluate the oil reserves contained in the fractured volcanic basement reservoir zone. The very hard (26,000 psi average compressive strength, with spikes of up to 50,000 psi) and abrasive nature brought drilling challenges, in particular, how to effectively and efficiently fail and fracture the rock. In a well in the previous drilling campaign, 10 runs of bit were required to complete the 294-m interval hole section containing basement formation. Various roller cone and PDC bit designs were utilized, with a resulting maximum penetration rate capability of 1.25 m/h and maximum run interval capability of 56.44 m. Another well with a basement interval of 463 m consumed 11 bit runs with maximum run drilling interval and penetration rate of 64 m and 1.56 m/h, respectively.

A conical diamond element (CDE) bit was proposed to achieve more efficient drilling in the basement. The 3D geometry of the conical diamond elements, which are placed across the bit blade, provided both a superior impact and wear resistance and concentrated point loading onto the formation; these characteristics enable the bit to cause failure and fracturing of the hard-to-drill rock more efficiently. A diamond layer in the bit is twice as thick as that of a conventional PDC cutter; this enhances impact strength and improves overall bit durability.

CDE bits were implemented to penetrate the basement formation in two different wells in Sumatera area. The wells were designed as directional J-type wells with maximum inclination of 70°. In the first well, eight-bladed and seven-bladed CDE bits were run with an excellent result of 131-m and 176 m of drilling interval achieved, respectively, yielding up to 211% of drilling meterage capability improvement (compared to the previous well). The rates of penetration (ROP) generated by CDE bits were also large; up to 4.17 m/h ROP was achieved (instantaneous on-bottom ROP reached up to 20 m/h), which was equivalent to 333% improvement. In the second well, the seven-bladed CDE bit generated 230 m of drilling interval with 3.27 m/h ROP, improving the offset well performance by 259% (in terms of interval) and 109% (in terms of ROP). The CDE bit significantly saved operating time and cost by improving the drilling speed and, most importantly, eliminating unnecessary trips to change the bit. The estimated potential savings from CDE bit utilization in these two wells reached more than USD 1.1 million.

The drilling optimization in Sumatera yielded insights into CDE design and features appropriate for basement application, and the engineering study behind the successful execution, actual drilling operation, and run performance comparison provided information for future such operations.
Study to Evaluate the Effect of Using Expansion Materials with Cement Slurry for High-Pressure/High-Temperature Wells
Authors: Shafqat A. U. , Taoutaou S. , Abdurrahman R. , Maksoud A. A. , Otaremwa L.
Published: October 2018

Oil and gas operators are facing more challenges than ever before to sustain production and to effectively minimize workover cost associated with remedial cementing. Previously, achieving the initial hydraulic seal with a good cement bond log was considered the only indicator of complete and durable zonal isolation throughout the lifetime of the well.

However, in a well drilled in a stressful environment, the initial zonal isolation can be jeopardized because of the changes in downhole conditions, primarily temperatures and pressures. Such cyclic changes in downhole pressures and temperatures generate radial cracks in cement and can cause the development of microannulus at casing/cement and cement/formation interfaces.

Extensive studies have been conducted in the past to understand the technical challenges to designing cement slurries with enhanced mechanical properties regulating the flexibility of set cement to withstand the stressful environment at downhole conditions. However, limited work has been done to evaluate the structural changes and impact on the set cement durability due to the requirement of expansion in set cement to eliminate the risk of microannulus.

A new methodology called industrial computed tomography is introduced to investigate the structural changes or cracks in set cement cured with various concentration of expansive additives. The novelty of this new methodology is that it represents a step change in defining the linear expansion requirement for given well conditions without jeopardizing the wellbore integrity.
Using Drill Pipe Connection Continuous Circulation Technology on a Geothermal Drilling Project in Indonesia to Reduce Stuck Pipe Events
Authors: Pinkstone H. , McCluskey T. , MacGregor A. , Scagliarini S. , Indrinanto Y.
Published: October 2018

A drill pipe Continuous Circulation Device (CCD) system was used by a geothermal operator in Indonesia, with this paper's scope as follows: Demonstrate CCD system performance used to successfully drill two wells to section Total Depth (TD) with reduced Non Productive Time (NPT) related to stuck pipe events;Highlight the engineering design modifications of the CCD system to cope with the harsh and challenging geothermal drilling environment, through the application of lessons learnt and the use of statistical data. These design enhancements to the CCD, provided a robust method for reducing drilling risks and improved operational performance.

The CCD system was used to successfully drill two wells: a total of seven hole sections were drilled from 17 ½" to 7 7/8" in diameter at two geothermal well sites in the same field, onshore Java. The use of the CCD system allowed the rig to maintain constant flow rate of drilling fluid down the drillstring during drill pipe connections. This is paramount to prevent stuck pipe events when total drilling fluid losses are experienced especially in geothermal wells due to their inherent subsurface geological complexity coupled with the risks of formation breakout collapse typical of geothermal well down hole environments. Maintaining dynamic wellbore conditions through circulation and maintaining constant hole cleaning prevents pack offs due to cuttings and formation breakout cavings, settling, and dropout.

The harsh geothermal drilling environment required the CCD system to be modified to operate with higher circulating flow rates and high levels of Lost Circulation Material (LCM) in a total mud losses scenario. The CCD system was developed accordingly through lessons learnt analysis and application, root cause identification, and management of change processes to provide engineered solutions, which were then field tested. The application of this technology improved project economics by reducing NPT related to stuck pipe events and helped in the avoidance of stuck pipe events escalation, resulting in expensive fishing jobs and, potentially, Bottom Hole Assemblies (BHA) lost in hole with consequent sidetracks and associated cost impact.
High Definition Reservoir Multi Boundary Mapping Delivered Highly Productive Horizontal Well in Challenging Clastic Reservoir and Faulted Area
Authors: Rane Nitin , Alshammari Baraa Sayyar , Al-Sabea Salem , Wenang Martine , Juyal Mukul , Keot Chandan Jyoti
Published: October 2018

With the advent of new age real time drilling technologies, the amount of data generated downhole has increased tremendously. Complemented by superior telemetry, the ability to transfer data uphole has increased by many folds too. With the introduction of new generation geosteering and reservoir mapping applications, it is possible now to integrate conventional logs with deep directional electromagnetic resistivity and advance formation evaluation measurements for accurate bed mapping, real time assessment of reservoir quality, structural dip calculation and forward planning trajectory – all in an integrated and single platform. The result is informed decisions and highly optimized results. The paper will discuss on a case study using this innovative integrated platform where geologists, drillers and geosteering engineers worked in sync to come up with the best possible real time decisions for optimum well design and placement, in a clastic reservoir, reducing overall well construction risks and negotiating the challenges of undesired geological events like trajectory drilling through a fault.

The interpretation of deep directional electromagnetic propagation measurements via highly sophisticated inversion algorithms gives information on the spatial position of the wellbore w.r.t reservoir boundaries. The remote detection of boundaries up to 20 ft around wellbore, gives us the edge for trajectory forward planning by predicting upcoming structural trend, in other words called Proactive GeoSteering. Conventional logs combined with high end measurements like spectroscopy, sigma, source less density and neutron provide accurate real time formation evaluation while drilling which enhance decision making of geo-steering process. Availability of these high-end technologies would allow operators to place horizontal well as close as possible to top reservoir, optimizing long term well performance by minimizing attic oil and delay water production.

The case study represents how latest state of the art real time drilling technologies coupled with advance geosteering techniques successfully helped overcoming various geological uncertainties encountered while drilling a horizontal well. Unexpected minor sub-seismic fault was successfully mitigated which avoid undesired non-productive time and lost productivity of the well. The results were very encouraging in terms of well production, and optimum placement of the horizontal well which will enhance long term recovery.

This paper provides new insight on successful application of multi boundary mapping technique in optimizing well placement in top part of the reservoir and offers approach for drilling horizontal wells in similar case of complex clastic reservoir. The technique also discusses mapping of sub-seismic faults that cannot be identified by normal seismic data, and how to mitigate subsequent risk of the fault.
A Coupled CFD-DEM Numerical Study of Lost Circulation Material Transport in Actual Rock Fracture Flow Space
Authors: Feng Y. , Li G. , Meng Y.
Published: October 2018

Fractures are beneficial to the cost-effective development of unconventional reservoirs, which may also induce drilling fluid loss, formation damage and other issues. Fracture plugging is the most common measures to settle those problems. The effect of fracture plugging largely depends on the lost circulation material (LCM) formula. In order to form the plugging zone rapidly in the near wellbore portion of fracture, it is necessary to study the transport process of LCM in real fracture. In this paper, the distributions of fracture aperture of a tight sandstone specimen are captured utilizing the high-resolution and high-precision structured light scanning systems, which is used to reconstruct the geometric model of actual rock fracture flow space. The coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) simulation is carried out to study the interaction between drilling fluid and LCM particles as well as LCM transport in above geometric model with various particle size. The constant directional torque (CDT) model is employed in the part of DEM computation to account the influence of LCM particle shape. The numerical simulation results show the LCM particles would plug in the narrow region of the actual rock fracture flow space, inducing the rapid accumulation of other LCM particles. The compatibility between the distributions of fracture aperture and the size of LCM particles played a decisive role in the transport process of the LCM particles, which directly determined the position of plugging zone. The multigrain bridging phenomenon of small size LCM particles was observed in simulations. This paper presents the idea of combining the reconstruction technique of actual rock fracture flow space and the CFD-DEM simulation to mimic the transport process of LCM particles in real rock fracture. The simulation results show the fracture surface topography has a significant influence on LCM particles transport and plugging zone distribution; the LCM particles considering the nonsphericity may multigrain bridge in the fracture which will greatly improve the efficiency of fracture plugging.
Conical Diamond Element PDC Bit as a Breakthrough to Drill Hard Geothermal Formation in Indonesia
Authors: Gunawan Fatah , Krisnanto Widoyo , Mardiana M. R. , Noviasta Bonar , Febriarto H. B.
Published: October 2018

In geothermal drilling application, one of the challenges faced by drilling engineers is the optimization of drilling bit which govern the key success of drilling performance. It should be aligned with recent key performance indicator such as meet the subsurface target comprehensively while optimizing the drilling cost. A typical formation in geothermal wells that consists of various types of volcanic and igneous rock should be identified carefully because the high range of hardness and abrasiveness value will respectively affect the bit. Hence, the improvement of conventional drilling bit should be carried out to enhance the drilling performance.

For so many years, Tungsten Carbide Insert (TCI) bits were implemented in the geothermal drilling application because it is believed to be the most effective bit to drill hard formation. However, the TCI bits are limited by the maximum revolution the bit can achieve before the bearing seal fails. In some application, it needs 3 to 4 TCI runs to finish 9.875-in section. Some of the bits were also pulled out of the hole with undergauged condition due to formation abrasiveness. Implementing a conical diamond element (CDE) on a PDC can increase the bit durability. CDE provides significant improvement of wear and impact resistance to the bit. The point loading of this cutter is more concentrated to the formation, allows the bit to remove the rock in more efficient way. It has been discussed that the CDE bit can improve the ROP and meterage drilled, eliminating the tripping time due to bit changes as it does not have KREV limitation, and has a better trajectory control.

Usually, 3-5 TCI bits were used to drilled 9.875-in section in one of geothermal well located in Hululais Field, Sumatera, with average meterage of 200 – 250 m per bit. Drilling dynamics FEA modeling was performed prior to the run of CDE bit to check the drill string vibration and provide stable drilling parameter roadmap for this bit. A CDE bit was run to drill this section and the result was excellent by drilling 600 m in a single run. The ROP was improved by around 35% compared to the maximum TCI's ROP. The bit generated less reactive torque fluctuation compared to TCI, allowed the bit to have better directional control. The CDE bit was pulled out of the hole with good dull grading (2-1-WT-A-X-I-CT-TD). By improving the ROP and eliminating the tripping time, the drilling cost can be reduced.

With the downturn of oil and gas business, geothermal projects in Indonesia is raising. CDE bit is becoming a breakthrough to optimize the drilling operation in by substituting TCI runs with huge amount of potential cost savings.
Development of a New Mathematical Model To Quantitatively Evaluate Equilibrium Height of Proppant Bed in Hydraulic Fractures for Slickwater Treatment
Authors: Hu Xiaodong , Wu Kan , Song Xianzhi , Yu Wei , Zuo Lihua , Li Gensheng , Shen Zhonghou
Published: October 2018

The proppant bed develops and its height grows until it reaches the critical velocity and equilibrium height. This paper proposes a comprehensive mathematical model to evaluate the equilibrium height for slickwater treatment. We use well-accepted published experimental data and models from other groups to validate our model. After that, we investigate the effects of proppant properties and fluid properties on the equilibrium height. This work can provide critical insights to optimize the design of proppant parameters in a hydraulic fracture. Meanwhile, this model can be incorporated into fracture-propagation simulators for simulating proppant transport.
Insights Into Rock Typing: A Critical Study
Authors: Ghanbarian Behzad , Lake Larry W. , Sahimi Muhammad
Published: October 2018

Various methods that link a representative pore-throat size to permeability k and porosity ϕ have been proposed in the literature for rock typing (i.e., identifying different classes of rocks and petrofacies). Among them, the Winland equation has been used extensively, although when it was first proposed, it was based on experiments. Because of its empiricism, the interpretation of the parameters of the Winland model and their variations from one rock sample or even one rock type to another is not clear. Therefore, the main objectives of this study are (1) to propose a new theoretical approach for identifying rock types that is based on the permeability k and the formation-resistivity factor F and (2) to provide theoretical insights into, and shed light upon, the parameters of the Winland equation, as well as those of other empirical models. We present a simple, but promising, framework and show that accurate identification of distinct petrofacies requires knowledge of the formation factor, which is measured routinely through petrophysical evaluation of porous rocks. We demonstrate that, although some rock samples might belong to the same type on the k-vs.-1/F plot, they might appear scattered on the k-vs.-ϕ plot and, thus, could seemingly correspond to other types. This is because both k and F are complex functions of the porosity, whereas the porosity itself is simply a measure of the pore volume (PV), and does not provide information on the dynamically connected pores that contribute to both k and F. We also show that each rock can be represented by a characteristic pore size Λ, which is a measure of the dynamically connected pores. Accurate estimates of Λ indicate that it is highly correlated with the permeability.
The Description and Quantification of the Truncation Errors Produced by Local-Grid Refinement in Reservoir Simulation
Authors: Tijink Paul , Cottier Juan
Published: October 2018

Geologically realistic 3D models yield nonorthogonal simulation grids as a result of grid distortion at faults, steeply dipping horizons, and zonal truncations. Finite-difference (FD) simulators applying discretization principles and volumetric flux calculation use two-point flux approximation (TPFA). On nonorthogonal grids, the TPFA causes numerical errors in the solution of pressure and saturation such that simulation results become inaccurate. These inaccuracies are known as grid-orientation effects.

This paper will demonstrate that TPFA applied to grids containing local-grid refinement (LGR) causes identical numerical errors. In the case of a vertically partial LGR, the numerical errors become so severe that they invalidate the simulation results. These results include unphysical oscillations in the fluxes within the LGR and unphysical baffles to flow at the interface between the coarse grid and the LGR.

The invalidation of simulation results is demonstrated by two case studies involving the history matching of well tests. To avoid invalid simulation results, any LGR applied in a grid must be extended over the entire vertical extent of the grid such that there exists no TPFA between the coarse- and the refined-grid cells in the vertical direction.
Elevated-Temperature and -Pressure Tribology of Drilling Fluids Used in Oil and Gas Extended-Reach-Drilling Applications
Authors: Lan Pixiang , Polychronopoulou Kyriaki , Iaccino Larry L. , Bao Xiaoying , Polycarpou Andreas A.
Published: October 2018

Extended-reach-drilling (ERD) wells are expensive and challenging; however, in special situations, compared with conventional drilling, ERD wells are more environmentally friendly and cost-effective. Application of drilling fluids with good lubrication for ERD is one of the most important methods to facilitate longer total depth (TD) of the wells. To better simulate the elevated-temperature environment in the borehole, this study proposes a method to perform tribological studies of drilling fluids at temperatures higher than 100°C by conducting experiments in a high-chamber-pressure environment, which can suppress the evaporation of the drilling fluid at high temperatures. Two lubricant additives were studied, and the results showed that, for the drilling fluid at elevated temperatures, a prototype additive (Additive A) reduced the coefficient of friction (COF) significantly by 44.8%, whereas a commercial additive (Additive B) caused only a slight reduction of the COF by 4%. After the tribological experiments, the wear mechanisms of the additives and abrasive particles were investigated with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).
Optimizing Jet-Pump Production in the Presence of Gas
Authors: Kurkjian Andrew L.
Published: October 2018

A hydraulic jet pump with both gas and liquid phases at the intake is modeled analytically. A complete system model results when this is combined with models of the surface pump, tubing, casing, and the pressure/temperature behavior of oil and gas. This model is used to size jet pumps before installation and to optimize production. Production optimization includes first estimating the pump-intake pressure and then determining the drive frequency for the surface pump that minimizes the pump-intake pressure. There is an optimal frequency at which the intake pressure is minimized and production is maximized.