Objective/Scope: Advanced geo-navigation technique in multilateral wells is currently being used to optimize oil production from a number of reservoir zones in Mauddud formation in the ongoing development of Sabriyah oil field. Multilateral wells generally help reduce cost of hydrocarbon production and are known to perform better than single horizontal wells. However, the application of appropriate geo-navigation strategy and downhole logging-while-drilling (LWD) technologies to achieving maximum reservoir exposure is key to production outcomes. Well-ML was planned as a multilateral well with two horizontal drain sections LAT-0 and LAT-1, each targeting multiple reservoir zones MaB, MaC and MaD in Mauddud. The main objectives of the two horizontals was to place the wellbores in the more porous and less dense sections of the targeted reservoir zones, achieving 30 - 45%, 10 -15% and 50 - 60% of reservoir footages in MaB, MaC and MaD respectively. The variation in the reservoir depositional facies and structural uncertainties due to the presence of a major fault pose geosteering challenges, also risking not achieving the require reservoir footages in the targeted Mauddud reservoir zones.

Methods, Procedures, Process: A geo-navigation model was created using offset well gamma ray, resistivity, bulk density and neutron measurements. Petrophysical evaluation of simulated curves from LWD tool responses along the wellbore trajectory was used to optimize the location of the horizontal wells in the targeted reservoir zones. Selection of BHA tool was based on the degree to which simulated curves from specific LWD tools displayed identifiable response to variation in reservoir facies and structural character. The implemented BHA comprised of the rotary steerable system, azimuthal deep resistivity "distance-to-boundary" technology, and the near bit density-porosity.

Results, Observations, Conclusions: The enhanced geo-navigation technique of integrating the near-bit-density-porosity and the azimuthal deep resistivity distance-to-boundary tools played a major role in navigating the wellbore within the sweetest spot of the multiple reservoir zones with confidence. Percentage footage achieved in MaB-MaC-MaD was 49%- 14%-37% in LAT-0 and 34%-17%-49% in LAT-1. The positioning of the density/porosity sensors close to the drill bit reduced the reaction time to mitigate the challenges posed by abrupt changes in reservoir density/porosity characters and allowed for an earlier estimation of reservoir structural dips, particularly in MaC zone where there was poor azimuthal sensitivity in the deep resistivity measurements. The successful and continuous real-time geo-navigation operation resulted in an optimized production outcome that is 3 times the production from single horizontal producer recorded in the same multiple reservoir zones.

Novel/Additive Information: Enhanced geo-navigation technique in multilateral well targeting multiple reservoir zones.

Umm Ghudair Field is one of the major oil producing fields in West Kuwait. Oil was discovered in 1962 in the Lower Cretaceous Minagish Oolite Formation and more than 200 wells have been drilled to exploit this reservoir since then. Stratigraphically, the formation is defined by three units; Lower, Middle and Upper. The lower and upper units are considered non-reservoirs, while the middle one is hydrocarbon bearing. However, because of the continuous production over the past 50 years, the filed started to show a variable rise in its oil water contact (OWC). Consequently, this uncertain OWC rise has impacted the planning and production of the newly drilled wells (deviated and horizontal). Several recently drilled wells showed water breakthrough much earlier than expected.

To address this challenge and with an attempt to proactively predict the current OWC depth in the new wells to be drilled, Kuwait Oil Company (KOC) decided to try the new High Definition Reservoir-Mapping-While-Drilling (HD-RMWD) technology in one of the horizontal well in their field. The objective was to assess the potential of the technology in detecting and mapping the current OWC while landing the well in the target. Due to the ultra-deep detection range of the technology (in excess of 200 ft), the landing point could be adjusted proactively and early enough to accommodate any unexpected OWC depth changes in the field.

Kuwait Oil Company (KOC) offshore exploration and development plans are underway to boost its production capacity to the future target rate. However, the selection of offshore field development scheme is critical due to the associated flow assurance risks, which impact project economics, safety, and sustainability. The objective of this study is to simulate and evaluate two offshore field development schemes, namely subsea multiphase flow, and platform schemes. The evaluation is based on the associated flow assurance risks, project economics, and environmental impact of each development schemes. The analysis covers simulation of each scheme, prediction of flow assurance risks, and prevention/mitigation of the risks during the entire life of the field. Results revealed that although the flow assurance risks in the subsea multiphase flow scheme are significant, it eliminates the large investment cost of platform, which improves the project economics significantly, and minimize environmental impact. Conversely, although the platform development scheme has low flow assurance risk, platform capital investment cost may impair the project economics, safety, and environmental impact. This study investigates each scheme by simulating, economically evaluating, and environmental impact assessing both schemes, to enable the right decision and selection of field development plan.

Maximizing oil recovery is a very challenging assignment to oilfield operators worldwide. This requires additional and continuous adoption of new technologies and best practices. Water flooding is one of the most reliable recovery technique and been used for many years around the world to pressure support to the reservoir and minimize the bypassed oil in depleted reservoirs with no aquifer support.

This paper is presenting a case of well that was drilled and completed as a dumpflood well to provide pressure support to an oil-bearing zone that contributes most of the field's production. Dumping rates have showed poor performance due to near wellbore damage since completion. Many conventional stimulation trials were carried out with no sustained success. The well was selected for an advanced acid stimulation technique to improve the dumping rate by using the concept of Oscillating Fluid Injection. This process achieves deeper treatment penetration and more uniform fluid distribution. Root cause analysis, core analysis and well history have been used to optimize the job procedures and acid recipe to remove the suspected damage. The above-mentioned process treated the target zone with the same acid recipe that has been used in the previous conventional acid stimulation job.

The results of this advanced process showed a significant improvement in well injectivity compared with previous acid stimulation techniques. The post treatment evaluation showed an increased dumping rate by two times. The increased flowing bottomhole pressures observed in the surrounding producing wells confirm the direct benefit of the improved injectivity and consequent pressure support. These promising indications have opened new production optimization opportunities in the nearby wells to add significant oil gain.

This paper presents an unconventional method of acid stimulation technology in the improvement of injectivity in surface injection and dumpflood injectors compared with conventional techniques. This technology has opened new opportunities for improving the injectivity of the dumpflood wells, and go for full field implementation to maximize the oil recovery from depleted reservoir.

Cementing the 7″ liner in UG field has always posed a great challenge due to the poor cement bonding across the target production zone, Minagesh Oolite. This is due to the high water influx, from the proximity of the aquifier drives to the production zone, hence leading to contamination of the cement slurry during the cementation. This has resulted in the loss of zonal isolation in addition to the unwanted water production. Water cut production has been observed to rise from 30% upto 70% and 90% within the course of less than 10 years. This has burdened a major Middle East operator with increased cost associated with remedial cementing jobs & disposal of water. Furthermore, conventional water shut off techniques, including cement plug back techniques, were proven to be largely ineffectual, hence an efficient control method was sought out as an alternative.

This paper discusses the implementation of an optimized, fit for purpose cement slurry, with enhanced mechanical and self-repairing properties along with the operational optimization in West Kuwait UG field which has improved the overall cement quality around the liner along with the reduction of water content (WC%) with production throughout a six month observation period.

An optimized, fit-for-purpose cement slurry system, with expansive and enhanced mechanical properties was developed and tested to simulate the conditions downhole during and after the 7″ liner cementation. Self-repairing, also known as self-sealing, and expansion properties in the presence of water and hydrocarbons were also tested by inducing fractures in the cement and observing the expansion and swelling capability in the presence of up to 90% water and only 10% hydrocarbon.

The self-sealing slurry was implemented in a step by step in a planned manner in UG field, with preset KPI's so as to evaluate the effect of slurry on water intrusion. Furthermore, operational execution and optimization was also considered to ensure a flawless cementing job execution.

Implementation of the first 3 self-sealing cementations of 7″ liner in UG field, showed great improvement in the cement bond log after 48hrs of cement placement. Further, the water cut in one case was reduced from 52% after initial testing to 24% and 22%, in subsequent 3 month and 6 month evaluation, respectively. This technology has also been used in other fields across Kuwait where water intrusion is apparent and different downhole conditions were observed. There is a large scope to use this technology as high water cut and poor cementation is a very common problem across different fields.

Pulsed-neutron capture (PNC) logs are commonly used to determine formation water saturation in cased-hole environments, often for time-lapse monitoring purposes. This paper describes a new diffusion-corrected sigma algorithm developed for a pulse neutron logging tool.

In southeast Kuwait, diffusion-corrected sigma log data was recorded in three wells using an array of four optimally spaced gamma ray detectors above a neutron generator. To calculate a diffusion-corrected sigma, an algorithm based on a dual exponential fit was applied to the time-decay spectrum of the near and far detectors. This calculation separates the formation and borehole decays. This approach provides an apparent formation sigma for the near and far detectors. The algorithm uses the near detector for final sigma, and a diffusion correction to the near sigma is determined by a function of a near-far sigma difference.

The diffusion-corrected sigma matched the expected results and provided a good statistical quality—even at high sigma values—because it is based on the near detector with its higher count rate, as demonstrated in the examples presented. Also, the formation sigma was independent of different borehole conditions in which the data was recorded. The final formation sigma results were compared to volumetric results from open-hole data (volume of shale, effective porosity and water saturation) and sigma calculated from open-hole volumetric using material balance. The PNC data recorded in the three wells allowed determination of the most recent oil-water contact (OWC) and update of water encroachment maps from the time-lapse monitoring. Comparing with previous sigma data recorded in these wells, it was concluded a normalization transform is not needed because R² value of the linear regression is close to 1.

The diffusion-corrected sigma algorithm using dual exponential fit showed that this technique was able to extract independent values for borehole sigma and formation sigma for each detector and to perform an accurate diffusion correction. This algorithm will provide reliable sigma values regardless of the borehole conditions in which the data was recorded.

Well control situation in high angle wells put challenging environment for the acquisition and interpretation of formation evaluation data on wireline. This case study puts a highlight on a new technology, which allows mitigating the well deviation and trajectory-related complications in addition to wellbore stability to acquire accurate wireline quality data, resulting in an improved completion design and an increase in production.

The discussed well was drilled and completed as a horizontal open hole producer in 1994. It showed unstable production and was put on schedule for re-completion to increase production. The planned fishbone well completion design implied high-resolution caliper data acquisition to ascertain the borehole geometry in detail. Moreover, a time-lapse water saturation analysis was mandatory. On the other hand, a considerable operational risk was associated with conventional wireline tools deployment, pushing the toolstring downhole. However, this risk was minimized using the new compact well shuttle system (CWS) which has all the logging sensors housed inside the drill pipe before they can exit it to the open hole at the start of the operations.

This conveyance method gave the drillers full well control, having the ability to rotate the pipe and even circulate mud in this 95-degree inclined, unstable well. Using open-end bit allowed reaming during RIH and POOH. Also, memory data acquisition allowed getting the required well log data in one run.

Consequently, the well objectives were achieved, and operational risks were minimized. Also, the total well cost was optimized without sacrificing data quality, which supported formation evaluation of Mauddud reservoir drain. Finally, this led to an efficient completion and production decision-making.

The advanced conveyance method discussed in this case study has been deployed in a Horizontal well within Mauddud reservoir (onshore Kuwait) for the first time, reduces the risk and cost of accessing high angle wells and wells with well control situation.

It is critical to manage the temperature rise seen in the electrical power system and submersible motor, in order to have an optimum Electrical Submersible Pump (ESP) run life. This paper presents a case study in which a solution was applied to better manage the heat rise seen in the ESP during operations, particularly in low flow applications, that has led to a measurable increase in ESP run life across the field.

A Middle Eastern Operator of ESPs had installed wells completed with Y-tools and ESPs that showed unusually high motor temperatures and shorter than expected system run lives. A study was conducted, and the remedial action implemented was to install a shroud around the Y-tool, reducing the flow space in the annulus thus increasing the velocity of fluid past the motor. The study compared the data gathered from the shrouded and non- shrouded Y-tool ESP installations to determine the effectiveness of the corrective actions.

Motor temperature is a function of bottom hole temperature, percentage load against nameplate, fluid properties, power quality and fluid velocity past the ESP motor. This study has shown that the shrouded ESP significantly increased the fluid bypass velocity (more than 1ft/sec) alongside the submersible motor to deliver the required cooling for stable, reliable operation. Unshrouded systems experienced higher motor and intake temperatures that is instrumental in the deterioration in the insulative properties of the electrical system and leads to greater current leakage with the passage of time.

This paper will provide full, detailed knowledge on shrouded Y-Tool systems that can be effectively applied for low flow rate production, allowing well bore full access for wireline or coil tubing jobs. Moreover, efficient motor cooling is provided by the higher fluid velocity and while providing a better pump performance, is expected to result positively in ESP run life.

Pulsed-neutron capture (PNC) logs are commonly used to determine formation water saturation in cased-hole environments, often for time-lapse monitoring purposes. This paper describes a new diffusion-corrected sigma algorithm developed for a pulse neutron logging tool.

In southeast Kuwait, diffusion-corrected sigma log data was recorded in three wells using an array of four optimally spaced gamma ray detectors above a neutron generator. To calculate a diffusion-corrected sigma, an algorithm based on a dual exponential fit was applied to the time-decay spectrum of the near and far detectors. This calculation separates the formation and borehole decays. This approach provides an apparent formation sigma for the near and far detectors. The algorithm uses the near detector for final sigma, and a diffusion correction to the near sigma is determined by a function of a near-far sigma difference.

The diffusion-corrected sigma matched the expected results and provided a good statistical quality—even at high sigma values—because it is based on the near detector with its higher count rate, as demonstrated in the examples presented. Also, the formation sigma was independent of different borehole conditions in which the data was recorded. The final formation sigma results were compared to volumetric results from open-hole data (volume of shale, effective porosity and water saturation) and sigma calculated from open-hole volumetric using material balance. The PNC data recorded in the three wells allowed determination of the most recent oil-water contact (OWC) and update of water encroachment maps from the time-lapse monitoring. Comparing with previous sigma data recorded in these wells, it was concluded a normalization transform is not needed because R² value of the linear regression is close to 1.

The diffusion-corrected sigma algorithm using dual exponential fit showed that this technique was able to extract independent values for borehole sigma and formation sigma for each detector and to perform an accurate diffusion correction. This algorithm will provide reliable sigma values regardless of the borehole conditions in which the data was recorded.