Comparison of the accuracy of pilot-drill-guided and fully guided implant surgery with dynamic navigation. In vitro model study

The aims of the present study are to measure and compare dental implant deviations with fully guided and pilot-drill-guided protocols using dynamic navigation systems in polyurethane models. The pilot-drill-guided group was determined to be the study group and included 12 implant applications. In this group, the pilot hole was drilled with navigation guidance, and the procedure was completed freehandedly. In the control group, all the drilling and implant placement steps were performed using the navigation system, and a total of 12 implants were placed. The pre- and postoperative images were compared to calculate the magnitude of implant deviation. The quantitative data of the two groups were compared using the independent-samples t-test and Mann-Whitney U-test. The analyses revealed that the length of the procedure significantly differed between the two groups (p < 0.001). The procedure duration was significantly shorter in the study group. The entry deviation values of the two groups were not significantly different (p = 0.079). The analysis revealed the apex deviation to be higher in the study group than in the control group (p = 0.003). However, the two-dimensional vertical apex deviation values of the implants were not significantly different between groups (p = 0.068). Angular deviation was determined to be significantly higher in the study group (p < 0.001). In the present study, all implants were successfully placed in the models using a dynamic navigation system. The results of this study may be useful for future clinical studies.

An Advanced Ultra-Deep Resistivity Mapping Sensor Reduced Reservoir Uncertainty and Eliminated the Need for a Pilot Hole for the First Time; A Case Study from Offshore Abu Dhabi

The high reservoir uncertainty, due to the lateral distribution of fluids, results in variable water saturation, which is very challenging in drilling horizontal wells. In order to reduce uncertainty, the plan was to drill a pilot hole to evaluate the target zones and plan horizontal sections based on the information gained. To investigate the possibility of avoiding pilot holes in the future, an advanced ultra-deep resistivity mapping sensor was deployed to map the mature reservoirs, to identify formation and fluid boundaries early before penetrating them, avoiding the need for pilot holes. Prewell inversion modeling was conducted to optimize the spacing and firing frequency selection and to facilitate an early real-time geostopping decision. The plan was to run the ultra-deep resistivity mapping sensor in conjunction with shallow propagation resistivity, density, and neutron porosity tools while drilling the 8 ½-in. landing section. The real-time ultra-deep resistivity mapping inversion was run using a depth of inversion up to 120 ft., to be able to detect the reservoir early and evaluate the predicted reservoir resistivity. This would allow optimization of any geostopping decision. The ultra-deep resistivity mapping sensor delivered accurate mapping of low resistivity zones up to 85 ft. TVD away from the wellbore in a challenging low resistivity environment. The real-time ultra-deep resistivity mapping inversion enabled the prediction of resistivity values in target zones prior to entering the reservoir; values which were later crosschecked against open-hole logs for validation. The results enabled identification of the optimal geostopping point in the 8 ½-in. section, enabling up to seven rig days to be saved in the future by eliminating a pilot hole. In addition this would eliminate the risk of setting a whipstock at high inclination with the subsequent impact on milling operations. In specific cases, this minimizes drilling risks in unknown/high reservoir pressure zones by improving early detection of formation tops. Plans were modified for a nearby future well and the pilot-hole phase was eliminated because of the confidence provided by these results. Deployment of the ultra-deep resistivity mapping sensor in these mature carbonate reservoirs may reduce the uncertainty associated with fluid migration. In addition, use of the tool can facilitate precise geosteering to maintain distance from fluid boundaries in thick reservoirs. Furthermore, due to the depths of investigation possible with these tools, it will help enable the mapping of nearby reservoirs for future development. Further multi-disciplinary studies remain desirable using existing standard log data to validate the effectiveness of this concept for different fields and reservoirs.

Integration Success Story in Shilaif Shale Oil from Vertical Pilot to Horizontal

The development of unconventional target in the Shilaif formation is in line with the Unconventional objective towards adding to ADNOC reserves. For future optimization of development plans, it is of utmost importance to understand and test and therefore prove the productivity of the future Unconventional Horizontal Oil wells. The Shilaif formation was deposited in a deeper water intrashelf basin with thicknesses varying from 600 to 800 ft from deep basin to slope respectively. The formation is subdivided into 3 main composite sequences each with separate source and clean tight carbonates. The well under consideration (Well A-V for the vertical pilot and Well A-H for the horizontal wellbore) was drilled on purpose in a deep synclinal area to access the best possible oil generation and maturity in these shale Oil plays. Due to the stacked nature of these thick high-quality reservoirs, a pilot well is drilled to perform reservoir characterization and test hydrocarbon type and potential from each bench. Fracturing and testing are performed in each reservoir layer for the primary purpose to evaluate and collect key fracturing and reservoir parameter required to calibrate petrophysical and geomechanical model, landing target optimization and ultimately for the design of the development plan of this stacked play. Frac height, reservoir fluid composition and deliverability, pore pressure are among key data collected. The landing point selected based on the comprehensive unconventional core analysis integrated with petrophysical and geomechanical outcomes using post vertical frac and test results. Well A-H was drilled as a sidetrack from the pilot hole Well A-V. This lateral section was logged with LWD Triple Combo while Resistivity Image was acquired on WL. Based on the logging data the well stayed in the target Layer / formation, cutting analysis data for XRD and TOC was integrated with the petrophysical results in A-H well. Production test results from subject were among the highest rate seen during exploration and appraisal of this unconventional oil plays and compete with the current commercial top tier analog unconventional oil plays. Achieving those results in such early exploration phases is huge milestone for ADNOC unconventional exploration journey in UAE and sign of promising future development.

Lessons Learnt from a Successful Sampling While Drilling Campaign Delivering Formation Oil Samples and Saturation Pressure Measurements in High H2S Carbonates

As island development strategies gain focus for capitalizing deep offshore assets, limitations like fixed slot location bring about the need for drilling extended reach (ERD) wells with multiple drain holes and complex well geometry to maximize the reservoir coverage for increased production. Pressure testing and reservoir fluid sampling operations require long stationary time and pose a risk of differential sticking. Deploying a pressure testing and fluid sampling tool into the drilling bottom-hole assembly (BHA) helps in maintaining well control through continuous circulation and providing measures to retrieve the tool by rotation and jarring in case of pipe sticking. This paper presents the successful deployment of sampling while drilling tools in three ERD wells drilled using water based and oil based muds to acquire representative formation oil samples from a high H2S carbonate reservoir. The formation oil samples were collected immediately after drilling the well to the target depth for limiting the invasion to collect clean samples in shorter pump-out volume and time. After securing the samples, a phase separation test was performed by fluid expansion in a closed chamber to measure the saturation pressure of the oil. A 30-min long pressure build up was also performed for pressure transient analysis to estimate permeability. Formation fluid samples were collected, while pulling out the drilling BHA, within 12-48 hours of drilling the well by pumping out 100-170 liters of fluid from the formation in 4-6 hours. During clean up, absorbance spectroscopy identifies the fluid phases – gas, oil and water. Prominent trends observed in compressibility, mobility, sound slowness and refractive index measurements add confidence to the fluid identification and provide accurate contamination measurements. Single-phase tanks charged with nitrogen were used to assure quality samples for PVT analysis. The sample tanks are made of MP35N alloy and the flow lines are made of titanium that are both H2S resistant and non-scavenging materials and hence, a separate coat of non-scavenging material was not required. In highly deviated wells, sampling while drilling technology can close the gaps of the conventional wireline operation on pipe conveyed logging in addition to saving 5-days of rig time by eliminating the need for conditioning trips, a dedicated run for pressure testing and sampling and minimizing the risk of stuck pipe and well control incidents The results from downhole fluid analysis and PVT lab are compared in this paper. Going forward, this technology can eliminate the requirement of a pilot hole for pressure testing & sampling by enabling sampling in complex well geometries in landing sections and ERD wells. The paper concludes with discussions on suggested improvements in the tool design and capability and recommendations on best practices to align with the lessons learnt in this sampling while drilling campaign.

Biomechanical Comparison of Fixation Stability among Various Pedicle Screw Geometries: Effects of Screw Outer/Inner Projection Shape and Thread Profile

The proper screw geometry and pilot-hole size remain controversial in current biomechanical studies. Variable results arise from differences in specimen anatomy and density, uncontrolled screw properties and mixed screw brands, in addition to the use of different tapping methods. The purpose of this study was to evaluate the effect of bone density and pilot-hole size on the biomechanical performance of various pedicle screw geometries. Six screw designs, involving three different outer/inner projections of screws (cylindrical/conical, conical/conical and cylindrical/cylindrical), together with two different thread profiles (square and V), were examined. The insertional torque and pullout strength of each screw were measured following insertion of the screw into test blocks, with densities of 20 and 30 pcf, predrilled with 2.7-mm/3.2-mm/3.7-mm pilot holes. The correlation between the bone volume embedded in the screw threads and the pullout strength was statistically analyzed. Our study demonstrates that V-shaped screw threads showed a higher pullout strength than S-shaped threads in materials of different densities and among different pilot-hole sizes. The configuration, consisting of an outer cylindrical shape, an inner conical shape and V-shaped screw threads, showed the highest insertional torque and pullout strength at a normal and higher-than-normal bone density. Even with increasing pilot-hole size, this configuration maintained superiority.

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.

Casing While Drilling Level 2 as Mitigation for Shallow Gas and Loss Circulation Hazards in Surface Section

Casing while drilling Level 2 was introduced to mitigate problems in the surface section of Mutiara and Pamaguan Field in East Kalimantan. These two fields have historical shallow gas and loss circulation hazards in surface section. Following a blowout incident in Pamaguan in 2012, new policy was introduced for drilling the surface section in Mutiara and Pamaguan. A pilot hole must be drilled, and additional surface casing shall be set. Although considered safe, longer drilling days and vulnerability to repeated loss circulation made this method inefficient. A new approach to mitigate the problem was proposed by introducing casing while drilling Level 2 in 2020 drilling campaign. Many papers already discussed about the effectiveness of casing while drilling to mitigate loss circulation. However, a limited number of papers discuss casing while drilling to mitigate shallow gas. Costeno et al, 2012, discussed the use of casing while drilling to mitigate shallow gas. However, the risk of shallow gas was low and there was no shallow gas record during the execution. This paper specifically discusses about utilizing casing while drilling (CWD) technology to mitigate not only loss circulation, but also shallow gas risks during surface hole interval. Both hazards occurred in several wells during job execution and CWD with its plastering effect has managed to drill troublesome surface hole safely, thus making it the better alternative to achieve efficient drilling in comparison with the previously used pilot hole method.

HDD by Intersection Technique (Case Study): A Novel Approach

Horizontal Directional Drilling (HDD) is a trenchless construction technique used extensively in the installation of pipeline carrying hydrocarbons, water, sewage, cables etc., across obstructions where conventional trench and lay method or jacking-boring method cannot be suitably applied. HDD technique also minimises the impact of installation activities in densely populated and ecologically sensitive areas. HDD technique, however, has its inherent shortcomings which render it unsuitable in many real-world scenarios. The torque available at the mud-motor for driving and steering of the drill is fairly reduced for long length crossings. Also, maintaining the directional control of the drill bit becomes increasingly difficult for such long crossings. These shortcomings can be overcome using “Intersect Technique” by utilising electromagnetic steering technology for precise real-time tracking, wherein pilot holes are drilled from both ends using two separate drilling arrangements. On reaching the predefined intersection range, a virtual handshake between the drill bits is achieved. Thereafter, the primary rig continues the bore to the end of the design path to reach at the secondary rig side. The present case study discusses at length the execution of HDD crossing of 18”- 2523 metre multi-product pipeline alongwith 6” CS conduit for OFC of M/s BPCL across the Thane-Vashi Creek in Mumbai, India. The length of the crossing combined with the presence of numerous pipelines of various operators made the execution of this pipeline crossing by “Intersection Technique” as the most suitable methodology. The pipeline was laid at an average depth of 15 m below the lowest creek bed level in geology which primarily included weathered basalt rock. The pilot hole for the crossing was completed utilising ParaTrack® drilling guidance and tracking system.

Using XRF Elemental Data and XRD Direct Measured Mineralogy for an Accurate Wellbore Placement and Geosteering through Carbonates Reservoirs* Drilled Within 04 ½" Slim Hole: A Case Study from a Jurassic Middle Marrat Carbonates Reservoir-Kuwait

ABSTRACT As the pursuit of oil and gas in Middle East Jurassic carbonates reservoirs grows, it is increasingly evident that horizontal wellbore placement, or targeting, plays a first-order role in the production capability of a well. Indeed, the percentage of a wellbore "in target" is a common metric used when evaluating the causes for good or poor production from any particular well. The most common process used for geosteering a horizontal wellbore into a chosen target is the correlation of logging-while-drilling (LWD) total gamma-ray (GR) to a vertical pilot-hole GR log or offset wells GR logs. However, limitations inherent to this procedure can reduce the ability to effectively use LWD GR data due to 4 ½" slim hole diameter and mud telemetry issues, the non-descript signal from LWD tools due to high pressure and high temperature and the possibility of lost signal from LWD tools. In addition, the thickness of MRW-F11 targeted reservoir is limited to plus or minus 22 ft and low GR contrast from bed to bed might lead to loss of directional control in the target MRW-F11. To accurately geosteer a well, Geochemical analyses of drilled cuttings are proposed to assist well placement. The analyses performed were elemental data derived from energy-dispersive X-ray fluorescence (ED-XRF) and mineralogical quantitative content acquired from the direct measurement from energy-dispersive X-ray Diffraction (ED-XRD). The Elemental and mineralogy data were acquired from drilling cuttings taken at ten feet intervals, from two offsets wells. The mineral and elemental data were used to build a chemo-stratigraphic profile and zonation of the sedimentary section. Chemo-stratigraphic zones are defined as having multiple elements and keys ratios (where possible) which illustrate distinct changes in chemical and mineralogical composition profiles from one zone to another. These zones were correlated over reasonable distances (at a minimum the length of the horizontal wellbore) and can be readily identifiable in cuttings. Using these criteria chemo-stratigraphic zonation's have been constructed in the Middle Marrat formation going from MRW-F1 toward MRW-F11 layer. Well site ED-XRF and ED-XRD data were used in conjunction with LWD Gamma Ray to geosteer at approximately 22 feet thin zone which resides at the base of an approximately 100 ft thick reservoir carbonate section of the main MRW-F11 reservoir. The LWD GR Signal was 45 ft behind the bit while all XRF and XRD data were at plus or minus 5 feet while sliding at plus or minus 10 ft in rotary mode and with a controlled slow rate of penetration (ROP) of 10 ft/hr. Geochemical rock analyses (GEAR) using XRF & XRD chemical analyses was the unique reference for approximately 500 ft interval to geosteer the well when LWD lost the signal, wiper trip was cancelled which considerably reduced drilling costs. Well site XRF and XRD data was successfully applied to geosteer the well, determine the position of the wellbore in zones of non-descript LWD GR signature, and determine the lateral extent of the reservoir interval.