bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Techniques for Mapping Oil-Water Contacts
Authors: Taher A. , Fouda M. , Osman H. , Alotaibi A.
Published: February 2024

Lateral variation of water levels can pose a great challenge to successful placement of horizontal production wells. Continuous identification of water levels has been traditionally achieved by logging old vertical or deviated wells drilled in the area, or by drilling new ones for evaluation purposes. This process is usually costly, time-consuming, and does not resolve the lateral uncertainty between those wells. This paper discusses the effectiveness of traditional and advanced modern techniques for identifying varying water levels, for successfully placing horizontal wells in the reservoir.

Traditional techniques to identify water levels based on vertical or deviated well logs utilize resistivity data from logging-while-drilling (LWD) or wireline tools. The results of using different types and frequencies of LWD and wireline resistivity measurements were analyzed. In addition, LWD formation testing data were used for calculating pressure gradients to confirm fluid type and density, as well as estimate formation water salinity. While drilling horizontal sections, evaluation of the oil-water contact (OWC) can be achieved using 1D and 3D inversion from deep and ultra-deep resistivity tool measurements. This technique, using real-time data, provided good estimates of fluid boundary positions. Advanced 3D inversion techniques were also examined to distinguish between the lithology of layers with similar resistivity values.

Comparing the different modes and frequencies of LWD propagation resistivity has shown how evaluating water zones in deviated wellbores has several challenges, depending on which resistivity response is used for the evaluation. Calculating pressure gradients with LWD formation testers is shown to be a successful approach although challenges can be faced due to using different drawdown rates compared to wireline testers. For horizontal wells, real-time fluid mapping using deep and ultra-deep resistivity allowed the assessment of lateral variations of the OWC, making it possible to maintain a distance from the water contacts while drilling. The utilization of 3D inversion for resistivity and anisotropy helped to determine the fluid type and lithology at a distance, where anisotropy evaluation was the differentiator for situations where shale and water-bearing sand zones had very similar resistivities. Integrated data from multiple wells allowed mapping of the water level as a three-dimensional surface at a wide multi-well scale.

This paper presents an integrated approach to mapping OWCs using traditional and advanced techniques. The data used for single-well and multi-well analysis enabled proactive well placement as well as better planning of future wells.
Study on 4D Geomechanical Modelling for Fault Critical Re-Active Stress Evaluation in Underground Gas Storage
Authors: Zhou Daiyu. , Tang Yongliang. , Zhou Wei. , Wu Zangyuan. , Wu Yiming. , Yan Gengping. , Huang Zhaoting. , Wang Haiying. , Li Zheng. , Li Yang. , Lian Liming. , Zhang Liang. , Fu Ying. , Huang Xingning.
Published: February 2024

During the high-speed injection and extraction cycle of an underground gas storage reservoir, the pool's pore pressure, effective stress, and faults change periodically, which may cause formation damage and natural gas leakage, thus affecting the sealing of the entire reservoir. At the same time, the non-homogeneity easily causes local pressure accumulation, which makes the pore pressure and effective stress distribution extremely unbalanced, and the local pressure accumulation in the formation is a potential threat to the operation of the gas storage reservoir. At the same time, clarifying the fault stress field evolution can provide theoretical support for raising the upper limit pressure at a later stage. Therefore, the study of four-dimensional stress field evolution characteristics of the gas storage reservoir geologic body is directly related to the safe operation and efficient use of the gas storage reservoir. This paper investigates the evolution characteristics of fault stress fields in light of the characteristics of multi-cycle high-flow injection and extraction cycles in gas storage reservoirs. In this paper, numerical simulation is used to analyze the factors affecting the integrity of the fault. At the same time, gas-water two-phase seepage and flow-solid coupling principles are used to analyze the seepage mechanics and geomechanics of the conceptual model by combining with the integrated software of geoengineering. According to the simulation results, the pressure and stress fields with time and space changes and distribution characteristics were carried out, and the destructive prediction was carried out to find the submerged destabilized parts. A large-scale seepage-stress coupling field model was established based on the field data, and the model's accuracy was verified by simulation. Finally, seepage mechanics and geomechanical analysis were carried out for the actual model, and the results can provide theoretical support for the construction of the project and the adjustment of the injection and mining program in the later stage to improve the upper limit pressure.
Research on Intelligent Optimization of Intermittent Lift Systems for Low Production Oil Wells
Authors: Ma Gaoqiang , Yu Yanwen , Zhao Ruidong , Shi Junfeng , Wang Jianyu , Zhang Xishun , Chen Shiwen , Chen Guanhong
Published: February 2024

In later stages of production, the depletion of formation energy can lead to a severe shortage of fluid supply, causing oil wells to operate at suboptimal production levels and reduced efficiency. Intermittent lift, as an effective solution, can enhance pumping efficiency and reduce wear and tear on both surface and downhole equipment. To establish a practical intermittent lift system, it is crucial to have a precise understanding of the dynamic fluid level and its evolution. This paper addresses the fluid level and its relationship with time-series indicator diagrams, accounting for factors like changes in inertia, friction, vibration, pressure, and fluid properties. Based on this fluid level recovery/decline law, a self-learning and self-optimizing intermittent lift system is introduced, with the goal of maintaining the liquid level within a predetermined range while maximizing daily oil production per energy consumption. The optimal design of the intermittent lift system is centered on the fluid level. Comparative analysis with existing models, such as Zhang's and Li's models, reveals a significant reduction in the average error, from 30% to 11.6%, with the implementation of this new model. Following a thorough on-site analysis, a manual intermittent lift well is selected for the implementation of intelligent design. A comparison with the manual intermittent lift system demonstrates significant improvements. The duration of switching the well on and off is reduced from days to minutes, resulting in a 4.1% increase in system efficiency, a 36% reduction in power consumption, and a 0.16t increase in oil production. This paper introduces an intelligent intermittent lift system, facilitating the transition from manual to intelligent operations while ensuring consistent fluid level adjustments. Furthermore, the system can be optimized to align with electricity pricing fluctuations, leading to cost savings and increased operational efficiency, which has practical significance in enhancing intelligent manufacturing and refining management.
Using AHP and Stochastic TOPSIS for Carbon Storage Screening and Ranking with Uncertainty Analysis
Authors: Ma J. , Gennaro V. D. , Tan B.
Published: February 2024

A methodology is presented for screening and ranking potential carbon dioxide (CO2) geological storage sites, based on the classical carbon sequestration performance factors - capacity, injectivity, and containment. Other nontechnical criteria, such as cost and public acceptance, are also considered. The various criteria are not always quantitative, sometimes conflict, and can address different risks. Their relative importance may depend on the context.

The Analytic Hierarchy Process (AHP) is used to determine the relative weights of different decision criteria. It has the ability for quantitative and qualitative evaluation of attributes, enabling simple and effective determination of relative weights by comparing attributes in pairs. Next, the intuitive Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is applied to calculate site scores and rank sites by comparing each weighted criterion simultaneously for all sites. Monte Carlo simulation is used for uncertainty analysis of results. Finally, sensitivity analysis is provided to show how the ranking results will change when inputs vary.

The workflow was applied to field data from an existing project for carbon capture and storage (CCS) site screening and selection, which had ranked nine sites, using Excel-based score cards and 31 criteria that were chosen based on data availability. After weighting the criteria via AHP, a stochastic version of TOPSIS was used to score and rank the sites, as well as provide an uncertainty analysis. Comparison with the previous unweighted user-dependent approach revealed that the new workflow improved site ranking because the various criteria are assigned weights, and site properties are evaluated based on precise numerical values instead of a range of values. Moreover, the impact of each site property on different aspects of the project (e.g., economics, safety) can be examined. Unlike Excel score cards, where confidence and score are not correlated, uncertainty and sensitivity analyses in the new workflow indicate overall uncertainty of the results.

This novel integration of AHP for criteria weighting and TOPSIS for sites scoring improves the accuracy and efficiency of carbon storage sites selection. Introduction of Monte Carlo simulation assists the analysis of site properties uncertainty influence on final ranking results, which increases confidence in the final choice. Sensitivity analysis provides information on how ranking results will change when inputs vary, consequently guiding data collection next steps to reduce uncertainty and risk.
Overcoming Formation Stability Risks and Optimizing Drilling Time using Continuous Circulation System (CCS) for the First Time in the Colombian Foothills
Authors: Moncada J. , Zuleta O. , Tovar J. , Bacca M. E. , Martinez M. , Duran W. , Salcedo C. , Bastos H. , Moreno G. , Cuevas N. , Ospina J. M. , Martinez M. , Gutierrez J. , Ayala L. , Rueda M.
Published: February 2024

The largest oil and gas operator in Colombia often faces challenges when drilling in the Llanos Foothills oilfield because of the area's complex geology. Issues typically occur in the Carbonera Coal formation, which is characterized by the presence of fractures with equivalent coal permeabilities and high-pressure fluctuations during conventional drilling operations. These characteristics create operational complications, such as stuck pipe caused by cuttings and difficulty during wellbore cleanout caused by cuttings decantation or caving when circulation stops (Fig. 1).

Continuous circulation systems (CCS) help mitigate undesired wellbore geometrical effects and potential packoff during connections, which can save rig time and generate additional benefits, such as cooling of the measurement while drilling (MWD) tools and maintaining bottomhole pressure (BHP) control during drillpipe connection.

By using a CCS in the Llano Foothills, the operator reduced the operation by seven days and total capital expenses by 1.05%. Additionally, sidetrack drilling was avoided, which saved time and helped reduce carbon emissions by 204.9 TCO2e with no health, safety, or environmental (HSE) incidents.

The first implementation of this CCS in Colombia is discussed and highlights a novel way to plan and execute drilling projects with the geological components of the Llanos Foothills. This technology was successfully used in the C7 and C8 units of the Carbonera Coal formation and could potentially be used in other areas of similar complexity.
How Corporations Succeed by Solving World's Toughest Problems - Tackling Climate Change with an Elite Business Research Consortium and AI-Enhanced Leadership: Decision-Making Endeavor in the Face of Climate Change
Authors: Uddin Ali Khan Muhammad Affan , Louis Clifford , Manzoor Abdul Ahad , Ali Syed Imran , Laliji Shaine Muhammadali , Aun Ali Syed Muhammad , Haneef Javed , Abbasi Faiq Azhar , Khan Muhammad Sami , Tirmizi Syed Talha , Kamran Muhamad
Published: February 2024

This study aims to contribute to the success of corporations in addressing global challenges, specifically focusing on climate change. The primary objective is to enhance the heat resistance capabilities of materials crucial for geothermal energy extraction, a key renewable energy source with minimal carbon footprint. Presently, Iceland leads in global geothermal energy production, emphasizing the significance of optimizing extraction methods. Previous research faced challenges due to suboptimal material selection, hindering drilling to greater depths. This study proposes a novel solution—employing innovative material coatings on drilling bits and pipes, utilizing metallic compounds with exceptional heat resistance properties. The coating strategy involves leaving pipes uncoated up to a depth where they naturally withstand heat, with subsequent application for greater depths. This approach promises cost-effective materials capable of enduring extreme conditions in geothermal drilling, fostering higher drilling depths and cost efficiency. Implementation projections suggest significant facilitation of geothermal energy extraction, particularly in abandoned wells near tectonic plate boundaries, reducing extraction costs. The study underscores the societal benefits of tapping into indigenous renewable energy sources, emphasizing the minimal carbon footprint of geothermal energy. The proposed material-coating approach aligns with global efforts to combat climate change and presents a strategic decision-making endeavor for corporations to contribute to environmental sustainability.
Unconventionally Hydraulic Fractured Wells to Develop a Tight Sour Oil Reservoir a Case Study from Oman South
Authors: Harrasi A. M. Al , Kalbani M. Al , Ouyang Y. , Al-Khusaibi A. , Tobi K. M. Al , Lefeber T. , Smirnov D. , Al-Shabibi A. , Al-Jarradi S. , Harrasi A. J. Al , Ghammari A. Al , Saadi Z. Al
Published: February 2024

This paper summarizes the integrated technical learnings from success with unconventional hydraulically fractured producers in a tight silicate reservoir located in Southern Oman. It shows the results and development challenges from a project to extend the proof of concept into further field development, maturing commercial volumes, and meeting the project’s value drivers. The producing reservoir is more than 3,000 m deep, encapsulated in salt and over-pressured. It contains light, sour oil with H2S/CO2 contents of 1 and 2 mol%, respectively.

Two wells were fracked with unconventional fracs as a new trail to the field. Previous wells were completed with conventional fracs. The result was used to formulate a phased development plan and define optimum subsurface decisions. Frac parameters were matched in Ghofer using actual pumping data. Dynamic Compute Modelling Group models with frac models were then used to match well test and PLT results. These models were subsequently used to generate production forecasts and defining the optimum subsurface decisions such that the project remains cost-competitive within the company’s project portfolio.

The two first unconventionally fracked wells show promising results in this tight sour reservoir. Unconventional fracking created longer fractures than conventional frac mainly due to less fracture damage and proves to deliver economic and competitive oil rates. Guar-based gel creates thicker shorter fractures. High-Viscosity-Frication-Reducer (HVFR) creates thinner and longer fractures. With unconventional fracs, the number stages were increased versus conventionally fracked wells, increasing reservoir coverage by factor three compared to conventionally fracked wells, and producing five times more oil rate at higher Tubing-Head- Pressures. Optimal Unconventional frac design and well spacing and number were evaluated jointly. To further optimize frac design, along term trial plan will be implemented. The study shows that factors such as matrix permeability, frac heigh and half- length mainly impact recovery. The project went through multiple project milestones to evaluate and optimize the development and select optimum project decisions that best meet the project’s value drivers. The team optimized well number, placement & frac design, material, and completion.

This paper discusses the unconventional frac result in a sour reservoir with all related challenges and project decisions. The authors have summarized the results from the successful unconventional frac, and field development decision related to the subsurface, frac and well designs that should be taken in an integration way. The study outcomes can be learnt from and replicated in similar sour tight reservoir fields.
Well Placement Optimization for Avoiding Caves Using GANs and POMDPs
Authors: Kanfar Rayan , Halabi Lama El , Hall Tyler , Mukerji Tapan
Published: February 2024

Exploration for subsurface resources, such as groundwater and hydrocarbons, involves a high degree of uncertainty. This is because the spatial distribution of targeted resources and the geology of their overburden is largely unknown. In some areas, eogenetic caves known as banana holes overlay targeted resources. Because of pressure loss, drilling into these caves causes operational hazards that lead to project delays, well abandonment, and even loss of life. The goal of this paper is to formulate well placement as a sequential decision-making problem and solve for an artificially intelligent agent that avoids drilling into these types of caves. We formulate the decision problem as a partially observable Markov decision process (POMDP). To model the spatial uncertainty of caves, a Generative Adversarial Network is used. The generative model is trained based on a Light Detection and Ranging survey from San Salvador Island, Bahamas. To solve for a policy that recommends drilling actions, the Fast Informed Bound algorithm is explored. The proposed sequential approach for well placement is shown to recommend a sequence of actions that avoids drilling into caves and demonstrates the potential of POMDPs in this problem.
Case Studies of a Novel Digital Twin System for Real-Time Early Identification and Warning of Pipe Stuck
Authors: Zhang Jiawei , Wang Qing , Zou Lingzhan , Yu Jingping , Li Jijun , Yang Yun , Zhang Yang , Zhao Zhixue
Published: February 2024

Pipe stuck serves as one of the primary downhole accidents in drilling industry with consequences ranging from minor inconvenience to severe complications. Despite the variation on its cause and mechanism, this downhole accident could be prevented or avoided based on early identification of its unique symptom or data behavior, provided intervention or remediation measures are taken promptly. While conventional prediction or recognition methods, which rely on the fluctuation amplitude and curve trends of surface drilling parameters, are subject to user experience and human error, it's often the case that their timeliness cannot be guaranteed.

A novel digital twin system, based on the deviation of hook load, torque and SPP (Standpipe Pressure) from theoretical modeled values and ROC (Rate of Change) of these three actual parameters, is developed for real-time early identification and warning of pipe stuck while drilling. A PSRI (Pipe Stuck Risk Index) ranging from 0%-100% is proposed based on ROC and deviation for comprehensive evaluation regardless of drilling state. Both T&D and wellbore hydraulics models are adopted to model the theoretical hook load, torque and SPP within preset computing cycle. ROC and deviation thresholds, corresponding to three different risk levels as low (green), medium(yellow) and high(red), were obtained by using RFA (Random Forest Algorithm) based on data of historical wells with and without pipe stuck accidents.

Preventive or intervention measures are generally mandatory for on-site personnels or engineers once high-risk (red) alert is identified by the system. Several case studies are outlined to exhibit that the occurrence of pipe stuck accidents could be detected typically between 30 minutes and 2 hours ahead during back-reaming and tripping operations, which proved its potential for early identification and prevention of this downhole accident in real-time drilling.

Cost containment and operational efficiency could be created with system implementation as it helps to reduce analysis time and provide timely proactive action in real-time monitoring, which demonstrates that digital twin driven technique could better capture and utilize digital data to minimize NPT and optimize drilling.
Channel Characterization in Sandstone Formation Using Pressure Transient Analysis - A Practical Overview to Define Geological Attributes
Authors: Alawami Rahmah L. , Tello Gomez Adan H. , Moreno Sierra Ferney G. , Brohi Imad
Published: February 2024

Understanding reservoir systems is of significant importance in optimal exploitation, development plans and management strategies. Sandstone reservoirs consisting of stacked channel deposits are known for their heterogeneity and varying depositional facies adding to their complexity. This paper will focus on the characterization of sandstone reservoirs in channel environments using pressure transient analysis coupled with seismic attributes and stratigraphic features.

Proper channel mapping and precise predications of the spatial distribution of sand bodies is a challenging process. Pressure transient analysis can identify the existence of channel features, reservoir properties, extent of formation properties, and boundary conditions. However, linear flow identified in well tests does not predict the direction of these channels. The proposal integrates both static and dynamic reservoir data along with regional geological interpretation which plays a vital role in the proper characterization and modeling of these channel systems.

The findings of this study enrich a deeper reservoir understanding of the structural features’ extent, continuity and connection. Different pressure regimes were observed in both vertical and lateral directions showing the complex heterogeneity in between layers and irregular channel distribution patterns. This response is similarly exhibited in the reservoir flow capacity which resulted in abrupt shifts in reservoir characteristics as evident in the acquired pressure transient data. It is proposed to revise seismic attributes and the use of stratigraphic core data to validate the conceptual connections between this complex channel system. In addition, findings are used to re-distribute formation properties in order to improve future reservoir models.

The combined use of dynamic and static data improves the regional interpretation of challenging sandstone systems. Adequate understanding of the spatial distribution of the sand facies and reservoir properties ensures effective well placement and development strategies.
Customized Drilling Fluids Solutions for Challenging Geothermal Wells
Authors: Olivares T.
Published: February 2024

Geothermal wells are very challenging to be drilled due high temperature and the associated risks that involve this type of wells. In order to find the adequate solutions for the drilling fluid challenges on those type of wells, we did an extensive lab evaluation on multiple formulations, where we used our approved drilling fluids additives portfolio to customize the required water-based fluids (WBF) and invert emulsion fluids (IEF) formulations for high temperature wells. Wide lab testing on multiple WBF and IEF formulations were performed In-house, simulating the harshest conditions to properly customize the drilling fluids solutions for a Geothermal wells campaign. However, before start these geothermal wells campaign and after successfully lab testing verification, those formulation were implemented at the field in wells with Bottom Hole Static temperature (BHST) from 330°F (165°C) up to 450°F (232°C). Similarly, those drilling fluids were used to successfully drill, log and core across those challenging environments without any issue related to the thermal stability of the drilling fluids additives.

In some of the wells, WBF was essential due logging requirements, for those wells, we relied on improved synthetic polymer thermal stable up to 475°F (246°C) to control the fluid loss, with the addition of temperature stabilizers and oxygen and H2S scavengers to optimize the polymers thermal stability. Also, we did utilize Causticized Lignite (CL) and chrome free methyl ester of sulfonated tannin (CFMEST) for better results as thinner and to help to control the fluid loss. Another fundamental additive in the formulation was the pre-hydrated bentonite used to enhance the suspension properties to avoid barite sag issues and to enhance the hole cleaning.

Other wells were drilled with similar conditions for the Geothermal wells using IEF, for this type of fluid, efforts were established to formulate an innovative solution to the challenging high-temperature conditions in the studied area. The issues addressed included hole cleaning, hole instability for a narrow mud-weight window and reservoir damage. The strategy was based on the synergy of combinations between polymeric packages, emulsifiers, and filtration reducers of the engineered IEF formulations to build stable fluids and afford tight emulsion and fragile gel properties with minimal filtrations to the formations.

As conclusion, we were able to customize Drilling Fluids Solutions for the multiple’s challenges expected during the Geothermal Wells operations. The excellent performance of those customized WBF and IEF formulations were delivered through use of novel emulsifiers chemistry, customized polymeric additives, innovative temperature stabilizers and a new multi-functional additive for narrow margin conditions, in preparation for this wells campaign.
Real Time Optimization of Drilling Parameters During Drilling Operations
Authors: Hinaai Qasim Al
Published: February 2024

Drilling Optimization is a main drive to reduce overall well cost. The current practice of performing drill off tests, whenever the founder point is reached, increases the risk of reducing bit life, wasting rig time, and depending on crew competency to find the best parameters. In other cases drilling with maximum parameters might lead to stuck or bit damage as shown in (figure-1).This research study as part of my MSc thesis in Robert Gordon University (RGU) aims to present a tested technique of real time optimization of drilling parameters using multiple regression analysis with an 8x8 matrix and 8 variables. The objective is to establish relationships between different drilling parameters and design a real-time optimization system for achieving the best Rate of Penetration (ROP) in drilling operations. The model incorporates offset data and subsurface conditions to predict ROP with an accuracy of over 90% compared to actual ROP. Additionally, the model has been enhanced with a bit tooth wear model to optimize both ROP and the longevity of the drilling section.
Increasing Oil Production With Jet Pumps by Reducing Pressure Losses in the Jet Pump-Sliding Sleeve Coupling
Authors: Soria J. , Izquierdo A. , Córdova F. , López B.
Published: February 2024

The pressure losses in the jet pump–sliding sleeve coupling were calculated for the typical completions of wells that produce using hydraulic pumping in the Ecuadorian oil fields. A new jet pump was designed to minimize losses. The field test results showed a significant increase in well production compared to those obtained with a conventional jet pump. Several studies have proposed improvements in jet pump efficiency by optimizing the nozzle, throat, and diffuser geometry. However, they have not considered possible flow restrictions once the fluid leaves the jet pump and goes through the sliding sleeve where the pump is seated. Therefore, computational fluid dynamics (CFD) simulations were performed to analyze the flow through the pump–sliding sleeve coupling in completions with 3.5 in. tubing string and 3.5x2.81 in. sliding sleeves. The simulations were run for different discharge flow rates from the outlet of the pump diffuser to the entry into the annular space. Excluding the characteristic energy losses of Venturi systems, the largest pressure losses were found in the flow through the pump-sliding sleeve coupling. This is because the pump discharge is located below the ports in the sleeve, and to reach the annular space, the fluid must pass through narrow conduits generated by the closing sleeve. Pressure losses in this zone are greater than 40 psi and increase with discharge flow. With these findings, the jet pump was redesigned to align the discharge flow with the ports in the sleeve and minimize pressure losses. The new design was installed in the X1 well of the Ecuadorian state oil company, which was producing 2,318 BLPD with a conventional jet pump. The new pump was installed with the same nozzle-throat combination and was driven with the same hydraulic power. The reduction in pressure losses in the pump-sliding sleeve coupling resulted in a 9% increase in the production of the well. Sliding sleeves were not designed to hold jet pumps. Although this practice has facilitated reestablishing the production of wells with hydraulic pumps using the existing completion, the inefficiency of the pump-sliding sleeve coupling would not allow the productive potential of the wells to be realized. The new jet pump presented in this article eliminates these problems.
Novel Application to Estimate Cement Quality by Means of Elemental Spectroscopy Data
Authors: Tanjung Heri , Al-Fawwaz Abdullah A. , Ghonim Elsayed Ouda , Tran Han Ngoc
Published: February 2024

Pulsed neutron log (PNL) is well known for its main application to determine hydrocarbon saturation in cased-hole wells by means of neutron inelastic reaction with carbon and oxygen elements. However, the computed hydrocarbon saturation might be biased by the presence of hydrocarbon in the annulus between casing and formation, in which the cement is not evenly distributed. Cement quality analysis is important to complement the cased-hole analysis, not only to ensure the validity of the computed hydrocarbon saturation but also to provide valuable insights in term of drilling and workover to take necessary action in ensuring zonal isolation between reservoirs.

Despite the available technology for cement evaluation, elemental spectroscopy reading from PNL can also be used to give an insight about the cement quality in the annulus since the emitted neutrons from PNL also interact with other elements in the formation and near borehole environment such as silicon, calcium, iron, magnesium, etc. which can be detected and quantified in term of count rate. The quantification of inelastic response between emitted neutron and calcium nuclei from PNL can serve as an indicator to define cement quality in annulus.

This paper explains the proposed technique to determine the cement presence by utilizing the elemental spectroscopy reading of calcium since typical elemental composition of cement is dominated by calcium. First, the zones with good cement condition and engaged wellbore need to be defined from CBL and caliper data as reference zones. Then, elemental spectroscopy reading of calcium over these reference zones is used to create the estimated standard calcium spectroscopy response for the whole interval with the same completion feature. Poor cement quality or lack of cement volume is indicated whenever the actual calcium spectroscopy reading is significantly less than the estimated standard calcium spectroscopy response. The result is then validated using the available conventional cement evaluation log such as cement bond log (CBL) and variable density log (VDL).

This proposed technique shows satisfactory result in most of the observed intervals. However, it is suggested to perform this technique using multi-arm caliper in order to better simulate the annulus volume for cement identification using down-hole spectroscopy data. It is also advised to utilize the latest generation triple-detector pulsed neutron log to obtain more precise elemental spectroscopy measurement.
Offshore Geothermal: A Major Resource for a Stressed Planet
Authors: Bolton Rebecca , Crossley Rob , Fowler Alex , Peter-Borie Mariane , Drumm Elisha , Williams Mark
Published: February 2024

Extended Abstract

The IPCC's AR6 Synthesis Report issues a stark warning, emphasizing that the world's current efforts to combat climate change fall short in terms of pace and scale (IPCC 2023). As per the IPCC's assessment, the primary pathways for mitigating energy emissions until 2030 involve the continued expansion of wind and solar energy. Additionally, there is significant potential to reduce methane emissions during the extraction and use of fossil fuels, as well as to capture and store carbon emissions. The report also highlights other energy sources that could be scaled up without directly contributing to emissions by 2030. These include bioenergy with carbon capture and storage (BECCS), hydropower, nuclear power and geothermal energy.

Geothermal energy holds a unique advantage as it offers both heat and power generation capabilities, along with the potential for creating a variety of cascading uses. While geothermal energy is a proven and reliable baseload resource on land, its commercial development often faces challenges related to subsurface geological complexity. Onshore geothermal also faces problems of scalability due to the variable subsurface distribution of heat and permeability capable of delivering sufficient energy for power production.

At CGG, we have undertaken research into the possibility of expanding geothermal energy beyond our current technical and geographic boundaries in the long term. This paper is intended to draw the attention of geoscientists, businesses, and policymakers to the substantial, and more consistently distributed, geothermal resources available globally in offshore settings, with a particular focus on the Red Sea region.
Clustering Intermittent Pumping: A Novel Low-Cost Intelligent Producing Method for Multiple Wells Based on Edge Computing
Authors: Wang Cai , Shi Junfeng , Zhao Ruidong , Zhu Weiquan , Li Huan , Ding Kun , Zhang Xishun , Sun Yizhen , Yu Yanwen , Zhou Xiang , Liu Xiang
Published: February 2024

Intermittent pumping is an effective measure to reduce energy consumption and improve system efficiency for stripping wells. To date, a intelligent control cabinet for intermittent pumping usually contains one soft starting device which is used to lower the starting electric current in case of motor failure caused by frequent well restart. The cost of intelligent control cabinet is relatively high that limits the popularization of intelligent intermittent pumping.

Thus, a novel low-cost clustering intelligent intermittent pumping technology which enables multiple wells to share one Silicon Control Rectifier (SCR) soft starter and one set of intelligent terminals is proposed. A calculation method for the intermittent pumping scheme of single well was proposed based on the principle of material balance. Moreover, a reasonable clustering intermittent pumping schedule for multiple wells was optimized using particle swarm algorithm to avoid the risk of control cabinet failures caused by simultaneous startup of multiple wells. The above algorithms were embedded into the IOTs intelligent control terminal to realize real-time perception and optimization. The core circuit of the control cabinet is composed of the soft starting side branch in parallel with the main branches of all oil wells, and the control switches of all branch circuits are intelligently sensed and controlled by the edge computing terminal.

The pilot test of one cabinet controlling three intermittent pumping wells was carried out on a targeted oil production platform. Before optimization, the pump efficiency of the three wells is 28.8%, 36.2%, and 13.7%, respectively. The optimized production time of the three wells is 49 minutes, 118 minutes, and 104 minutes, respectively. The shut-in time is 311 minutes, 242 minutes, and 256 minutes, respectively. Automatic production is achieved through the clustering intelligent control cabinet. The application results show that the clustering intermittent pumping technology reduces the total cost of control devices for three wells by 68%. The electricity saving rate of the three wells is 61%, saving about 37000 yuan per year.

The novel technology of clustering intermittent pumping fills in the blank of intelligent intermittent pumping for multiple well and greatly promotes the intelligence of oilfield sucker rod pumping system.
Machine Learning-Enabled Classification System to Screen and Rank Horizontal Wells by Sidetracking Success Criteria
Authors: BuKhamseen N. Y. , Maucec M. , Aneddame A. , Mohammadi H. H.
Published: February 2024

Sidetracking vertical wellbores into horizontal laterals to avoid or delay water coning is a common practice in managing oil reservoirs under water flooding. Accurately predicting if the sidetrack would improve the performance of the well (i.e., reduce water production, increase oil production, or both) represents a vital information to decide whether it is optimal to sidetrack or continue with current vertical hole and withstand the increasing water cut. In this paper, we employ algorithms of predictive analytics and machine learning (ML) on a large synthetic but realistic data set of vertical bore-holes that were converted later into sidetracks in order to predict if a sidetrack would be a success. We classify the sidetracks using ratios of cumulative oil production aggregated over different periods of time of wells before and after the sidetrack. As success criteria differ depending on business objective, multiple models were built to account for the pre-set possible scenarios. The data-driven models built were based on a binary supervised classification (successful/unsuccessful) with very good accuracy, measured with Area Under the Curve (AUC) and Receiver Operating Characteristics (ROC) scores. A large number of predictors is initially used in our model, such as well location, well configuration, well completion, normalized production data, pressure data, as well as assorted petro-physical attributes, such as reservoir quality and average saturation indices. Through an exercise of recursive feature elimination, only parameters that contribute to improve the quality of prediction are retained. Results of several classification algorithms such as decision trees and support vector machines are being studied and compared. Several developed models with cross-validation are introduced to reduce bias and variance and to render better prediction results. Applying the model on a set of test simulation data, ML model predictions of success and failure cases conform with simulated data with high level of accuracy. Additionally, predictive models were found useful in identifying parameters that highly correlate with the success or failure of sidetracks. Final results showed an accuracy as high as 80% and an AUC of the ROC curve of 0.79.
Hydrocarbon Saturation Evaluation Behind Gravel Packing and Complex Completion Through Advanced Pulsed Neutron Logging
Authors: How L. H. , Cavalleri C. , Yusuf N. , Tolioe W. A. , Daud S. H. , Johare D. , Hendrawati M. S.
Published: February 2024

Gravel packing in the annulus between the screen and casing ensures the production of reservoir fluids without sand production. However, the effectiveness for controlling sand production and the permeability of the pack decreases over the years. It is important to quantify the gravel packing together with formation fluids saturation evaluation for production enhancement opportunities. From pulsed neutron logging (PNL), analysis of the expanded set of elements and minerals at high accuracy allows the quantification of gravel packing and reservoir fluid saturation simultaneously.

Between two PNL runs, the background gamma ray (GR) count is subtracted from the activated GR count. The gravel pack log is made from linear response between the good gravel section and the top of gravel or major void. Besides, from inelastic-capture measurements in gravel packs, the normalization of near detector inelastic silicon yield to the sum of silicon and iron yields is another effective gravel pack quality indicator. Later in the processing path for formation evaluation, different environmental corrections and elemental offsets are determined to remove the contribution of gravel pack, different borehole fluid, and casing and cement composition. Ultimately, the integrated interpretation of carbon-oxygen (C/O), Total Organic Carbon dry weight fraction (TOC), neutron porosity (TPHI) and fast neutron cross section (FNXS) enable accurate determination of formation gas, oil, water saturation condition behind gravel pack and casing.

In three examples presented in this paper, the gravel pack (GP) quality has been addressed and analyzed based on two different methods: the traditional GR counts difference between activated and not log, and the direct estimate of gravel presence and percentage from raw elemental concentrations being measured by the advanced PNL simultaneously to the other pulsed neutron and carbon/oxygen measurements. Understanding the gravel packing and the contribution from borehole conditions will help to reduce the uncertainties of log response and to compute reliable rock petrophysical properties and fluids saturation in the formation.

The prompt evaluation of these gravel pack logs can provide a more accurate understanding of borehole effects on the petrophysical answer. The information can also directly be used to determine the void in gravel pack completions. Further plan for void repair can reduce the formation damage resulting from fluid loss in the formation.
Innovative Application of Solid Degradable Particles Mitigates Plug Failure and Efficiently Enhances Acid Fracturing Plug and Perf Operation
Authors: Albuainain Faisal , Almulhim Abdulrahman , Farias Stefano , Anwer Ibrahim
Published: February 2024

This methodology presents an efficient implementation of solid degradable particles to address zone isolation failures in plug and perforation (Plug and Perf) acid fracturing operations, thereby facilitating proper zone stimulation without the need for subsequent well interventions using coiled tubing or wireline.

The novel approach centers on the utilization of multi-modal, self-assembling, and self-degradable solid particles to temporarily seal the void space created by an unset ball in a mechanical plug situated between two fracturing stages. The methodology encompasses techniques for identifying isolation failures from various perspectives and outlines the necessary adjustments to transition from conventional solid degradable particle usage to align with this new approach. Additionally, a comprehensive method is presented for readers to replicate this solution in similar scenarios.

Effective stimulation of tight gas carbonate formations, particularly in high-temperature, high-stress, sour environments with reservoir heterogeneity, poses significant challenges. In addition to meticulously studying reservoir properties to select the appropriate acid blend and diverters for stimulation treatment, the completion strategy plays a pivotal role in augmenting stimulated reservoir volume.

While Plug and Perf operations have proven to be an effective solution for zone isolation, they entail additional time and costs when interventions are needed, such as addressing an unset ball within the plug.

This study focused on a horizontal well with two acid fracturing treatments, considering similar formation properties, perforation strategies and treatment fluid volumes. Based on these comparable parameters, a series of analysis were conducted to validate communication between stages through the mechanical plug. Subsequently, the methodology involved the design and efficient pumping of an appropriate solid degradable pill to isolate the path to the previously stimulated zone. Several indicators of its effectiveness were observed, including a significant pressure increase once particles began bridging and sealing off the path within the plug, an overall higher-pressure response between stages, and a substantial difference in instantaneous shut-in pressure (ISIP). These observations corroborated the effectiveness of stage isolation achieved using self-degradable solid particles, ultimately resulting in the treatment of the new non-stimulated zone.

The innovative application of solid degradable particles presented herein represents a forward-thinking solution that enhances the efficiency of Plug and Perf operations. It obviates the need for additional wireline interventions to set new plugs and contributes to improved reservoir stimulation coverage—a critical factor for the commercial recovery of hydrocarbons in carbonate tight gas reservoirs.
Characterizing Unconventional Hydrocarbon Resources Through Geochemical Analysis
Authors: Alghamdi Abdulaziz , Hassan Amjed , Mahmoud Mohamed , El-Husseiny Ammar , Abu-Mahfouz Israa S.
Published: February 2024

This study presents the use of geochemical analysis in order to improve the evaluation of unconventional recourses. Several parameters were studied including total organic carbon (TOC), free hydrocarbon amount (S1), potential hydrocarbon (S2), hydrogen index (HI), oxygen index (OI), pyrolyzed carbon (PC), and total sulfur content (Total S). The main objective is to understand the relationship between all these parameters and to examine the impact of thermal maturation on the geochemical variables. Organic-rich shale samples were collected and used in this work. The shale samples were maturated at different temperatures and for various durations. The Rock-Eval analysis was carried out before and after each thermal treatment in order to capture the changes in the geochemical properties.

The obtained results showed that thermal maturation can significantly change the geochemical properties, reducing the total organic carbon, increasing the S1, and reducing the HI. A reduction in the total organic carbon was observed, the TOC was reduced from around 20 to 15 and 12 wt.% after maturating the shale samples at 250 for one and two days, respectively. While the S1 was increased by three times on average due to the maturation processes. The HI was reduced from around 800 to less than 350 due to the maturation revealing that the kerogen was converted into vaporized hydrocarbon which leaves the shale and leads to the HI reduction. The vaporization of organic matter led to an increase in the rock porosity by around 4 to 8 p.u. Overall, this study confirms the importance of integrating different geochemical properties in order to improve the evaluation of unconventional resources.
Super-Virtual Interferometry for Noises Elimination in Microseismic Datasets
Authors: Zhou Yicheng , Hanafy Sherif
Published: February 2024

In microseismic study, traces with low signal-to-noise ratio (SNR) are considered an intractable issue, especially in surface monitoring arrays. To alleviate this problem, we propose to use the supervirtual interferometry (SVI) approach to enhance the SNR of the recorded traces. The key idea is to generate diffraction gathers by convolving different traces, then calculate the common negative-positive pair gathers by correlation and convolution, and finally stack similar traces to obtain supervirtual traces with higher SNR. We tested the proposed method on 2D acoustic single-source and multiple-source cases.