bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation Using Low-Frequency Distributed Acoustic Sensing for Propagating Fractures with Shear and Normal Stresses
Authors: Reid T. , Zhu D. , Hill A. D.
Published: October 2023

Low-frequency distributed acoustic sensing (LF-DAS) at a far field observation well is a diagnostic tool for hydraulic fracture propagation using measured values of strain. To understand subsurface conditions with shear and normal stresses, a laboratory-scale hydraulic fracture experiment was performed to simulate the LF-DAS response to fracture propagation with embedded distributed optical fiber strain sensors under these conditions. The objectives of this research are to generate hydraulic fractures of known geometry when shear and normal stresses are present, measure the strain response along distributed fiber sensors embedded in the sample, and use the results to enhance the interpretation of LF-DAS data measured at observation wells.

The experiment has been performed on a uniaxially-compressed, transparent cube made of epoxy with a radial initial flaw angled non-perpendicular to the applied stress. The epoxy cube is 8-in in each dimension. Fluid was injected into the sample to generate a fracture with shear and normal stresses along the plane of the fracture. These experiments used distributed high-definition fiber optic strain sensors with tight spatial resolutions. The sensors were embedded at four different locations, serving as observation/ monitoring locations. Pressure and fracture propagation were also recorded. The measured strains were compared to experiments with purely normal stress components to understand how the zero-strain and zero-strain rate methods for fracture geometry can be applied to the studied case when shear stress on the fracture plane is introduced.

The experimentally derived strain and strain-rate waterfall plots from this study with shear and normal stresses exhibit a narrowing region of extension surrounded by compression as the fracture approached and intersected a fiber optic cable. However, unlike the experiments with purely normal stress on the fracture plane, the introduction of shear stress has created an asymmetrical strain signature over the fracture plane. The dominant strain response on one side of the fracture plane suggests the existence of a shear stress on the plane of the fracture. This information can be used in the field to reveal the stress status during fracture propagation and more realistically evaluate the fracture front.
Novel Hybrid Degradable Plugs to Enable Acid Fracturing at High Temperature High Pressure Conditions
Authors: Zhao L. , Ren J. X. , Yuan M. , Liu Y. , Liu H. L. , Zhou C. J. , Wang S. W. , Ren G. F. , Cheng P.
Published: October 2023

Current commercial dissolvable plugs have been found unsuitable when we hydraulic fracture extremely HTHP wells, especially with acid. Dissolvable alloys, the most popular materials, react too intensively in acid environment, and nearly all types of commercial protective coatings have been tested unsatisfactory due to inevitable defects/holidays. Additionally, they suffer from recrystallization issues that prevent plugs from dissolving. Thermoplastic Polyglycolic Acid (PGA) may have a significantly low degradation rate in acid, but its temperature rating is too low.

To address this issue, we developed a new kind of fiber-enhanced degradable polymer composite material based on thermosets, which offers high strength and temperature rating, as well as low dissolving rate in acid conditions. Thanks to synergic effect from degradable metal slip design, a novel hybrid dissolvable plugs has been developed afterwards, which can not only hold pressure in HTHP condition and dissolve readily afterword, but most importantly can be dissolvable readily with acid (mainly through dissolving of metallic slips) if plug is stuck or set prematurely during installation process, a requirement crucial to our clients to develop wells suffering from deformative casing issues. Advanced degradable thermoset developed in this work offers temperature rating above 150℃ due to its highly cross-linked molecular structure. It exhibits extremely high strength (20~30 ksi [138-207 MPa] in tensile) at elevated temperature, and its dissolving rate in acid (15% HCl) is marginally higher than that in brine water during 2 hrs. of acid fracturing operation. Novel hybrid plug, with cone made from this new material and slips from traditional dissolvable alloy, is rated to hold pressure above 9000 psi (62 MPa) at 120℃ in acid fracturing condition, and degrades totally within 2 weeks, successfully meeting field requirement for HTHP wells. In case of premature set, this hybrid plug can be uninstalled reliably within hours through dissolving its dissolvable metal slips via acid.

To the best of our knowledge, it is the first report of degradable thermoset composite material in downhole plug application, and the first totally degradable hybrid plug working at HTHP condition in our industry. This study could not only benefit oil and gas industry to hydraulic frac HTHP reservoir inaccessible before, but also provides a new functional material that should be potentially used in development of other advanced tools in applications including drilling, completion, work over, etc.
Simulation-Assisted Diagnosis of GOR Evolution in Carbonate Reservoir, Offshore Abu Dhabi, Undergoing Miscible Gas Injection
Authors: Khan M. N. , Mogensen K. , Altaf B. , Menchaca T. Felix , Allouti A.
Published: October 2023

A major reservoir, Reservoir A, in an offshore carbonate field in Abu Dhabi underwent a thorough development-concept selection process. The subsurface evaluation recommended miscible gas injection-based development as the most optimal process, and the reservoir is undergoing the miscible gas injection operation. Over the course of production, ‘Reservoir A’ is experiencing a gradual GOR increase. The GOR evolution could be the result of different physical mechanisms, such as production below bubble point, gas coning, or miscible gas breakthrough. In the latter case, it is not clear whether reservoir dispersion has smeared out the miscible displacement front to a point where miscibility is lost. The key objective of this work was therefore to develop a diagnosis methodology using numerical simulation to interpret the GOR response.

A 2D numerical, fine-gridded simulation with a producer-injector pair was set up to explore the following scenarios: (a) production below bubble point; (b) gas coning from the gas cap; (3) a perfect miscible displacement; (4) a perfect immiscible displacement; (5) a miscible displacement that turns immiscible due to dispersion; (6) a combination of the above. The key output parameters tracked included GOR and its derivative and the flowing bottom pressure at the producer. The different runs were then compared against each other and with the measured GOR response.

A fit-for-purpose surveillance strategy was adopted to help assess the effectiveness of the overall development strategy. Recently, tracer test results confirmed the arrival of gas production down the horizontal wellbore. GOR evolution trends were captured using the inline multiphase flowmeters. The comparison of simulation-based type curves with the evolving GOR trend along with the other subsurface attributes shows an initial indication of the production of swelled oil, followed by the injection gas breakthrough. This paper showcases the effectiveness of the proposed technique and the initial results of the analysis.
Teaching the Teachers of Montana about the Oil and Gas Industry
Authors: Hoffman Todd , Decker Neil , Lynch Richard , North-Abbott Mary
Published: October 2023

It is vital to increase awareness and knowledge of petroleum engineering and the petroleum industry to the next generation of potential workers. This paper provides information about a program to educate Montana middle and high school math and science teachers about the oil and gas industry. We desire that stakeholders from other states can use this program as a model to create similar courses.

The Montana Tech Petroleum Engineering Department organized and implemented a one-week short course with (1) classroom material, including hands-on examples to showcase various aspects of developing and producing oil and gas reservoirs, and (2) field trips to observe field production operations, a CO2 flood, and a refinery. Montana Tech joined with industry partners and regulatory agencies to provide relevant and meaningful content. The various aspects of the petroleum industry were discussed, including exploration, drilling, completions, production, facilities, artificial lift, and reservoir management. In addition, we covered sustainability, energy sources and uses, climate change, and potential solutions (e.g. CO2 sequestration).

A previous version of this course ran from 2006-2015 and was supported by our state's oil and gas commission. In 2022, it was restarted and updated with funding from Hess Corporation. It was hosted on the university campus with educational materials, field trips, and room and board provided at no cost to the participants. The new short course was an overwhelming success. The teachers learned about the oil and gas industry and took this knowledge back to their classrooms across the state of Montana. Another benefit for the teachers is that they received continuing education credits, which they need to keep their teaching certificates current. The value for Montana Tech and the petroleum industry is that young adults entering college or the workforce will have more knowledge about oil and gas operations since their teachers are better informed and pass on their experience. Based on the success from 2022, the program is scheduled again for the summer of 2023 and expanded to include high school guidance counselors.

This paper will expand awareness of our Teacher's Workshop so it can be easily implemented in other regions where this program could be beneficial. The paper contains the content, workflows, and potential pitfalls so anyone implementing a similar course can use what we have learned as a starting point.
A Data-Driven Approach for Stylolite Detection
Authors: Cheng Jingru , He Bohao , Horne Roland. N.
Published: October 2023

Stylolite is a specific geopattern that can occur in both sedimentary rocks and deformed zones, which could change porosity of the reservoir, modify the permeability, and even result in horizontal permeability barriers. Though there are many related studies to characterize this issue, most of them focused on experimental methods. In this work, we proposed a new approach for recovering geometrical information of the stylolite zone (including its size and location) based on neural network architectures including convolutional neural network (CNN), recurrent neural network (RNN) and attention, which could serve as a preliminary data-driven solution to the problem.

To simplify the problem, we first conducted simulation by building three-dimensional multilayer reservoir models with one stylolite zone. We considered both simplified cases with only a few homogeneous layers, and cases with heterogeneous layers to generalize our work. For the heterogeneous case, we extracted the permeability from SPE10 model 2, a commonly used public resource. Producing and observation wells in the model are at different locations and provide pressure and production rate data as inputs for the deep learning models, in the form of multivariant time series data. For homogeneous cases, after zero-padding and standardizing our inputs to tackle different-length data and features with different scales, we passed our dataset to a CNN-LSTM model. The two subnetworks are connected in parallel to combine the advantages of CNN in extracting local temporal features and the strengths of LSTM in capturing long-time dependency via self-loops. Models containing only a few CNN and LSTM models are also covered in our work as baseline models. For heterogeneous cases, a CNN-based model U-net and an attention-based model SeFT were introduced to enhance the performance.

On the homogeneous dataset, our CNN-LSTM model achieved a satisfactory performance and could predict the locations and sizes of the stylolite zone and outperformed the two baseline models. On the more challenging heterogeneous dataset, our baseline and CNN- LSTM models failed to deliver meaningful results. In contrast, SeFT and U-net showed success in the sense that we could successfully predict the locations of the stylolite zones.
Crisis Management Holistic Training with Immersive Technologies for Awareness and Preparedness of Oil and Gas Professionals
Authors: Kokkinos N. C. , Mitropoulos A. C.
Published: October 2023

Many previous technological accidents were primarily caused by human factor. The oil and gas (O&G) industry is interested in new methods for improving human response and safety. The scope of the current study is to assess the use of immersive technologies in awareness and preparedness of oil and gas industry's staff in emergencies and in crisis management. The training methodology based on a holistic sevenfold approach. In the beginning, the oil and gas professionals familiarize themselves with fundamental physicochemical phenomena of the O&G sector in a research laboratory. In the second stage, the examining phenomena are modelled and simulated. Then, the model is verified, validated and tested taking into account the real feedback from the laboratory experiments. Thus, the entire developed system turns into a process. The next step is the use of immersive technologies in order to scale-up the process by developing a virtual reality (VR) environment of the real field. The produced VR environment is then simulated into high-tech full-size facilities including a virtual control room, a drilling simulator, a virtual dispatch center and a VR onshore or/and offshore oilfield with wearable equipment. The sixth stage of the holistic training is the dynamic overall financial audit of the oil and gas plants implemented in real time. Finally, evaluation and certification of O&G professionals take place. O&G trainees were tested in various emergency what-if scenarios that were not friction products, but rather the results of long-term interviews with industry executives, field operators and control room operators, who involved in past dangerous incidents, near-misses, and accidents. The study found that human factor played a significant role in the outcomes of emergencies, with careless or negligent behavior often causing problems. In some cases, the teamwork of the participants was excellent, but in others, communication problems led to emergency shutdowns or evacuation alarms. To our knowledge, an in situ holistic approach of crisis management training using immersive technologies for awareness and preparedness of O&G professionals has been studied for the first time.
Downhole Temperature Estimation of a Growing High-Temperature Wellbore Using a Modified Drift Flux Modeling Approach
Authors: Wang N. , S. Khaled M. , Luu A. , Ashok P. , van Oort E.
Published: October 2023

Downhole temperature (DHT) estimation is very important for heat management while drilling high-pressure, high-temperature (HPHT) and geothermal wells to prevent premature bit and downhole tool failure. Existing transient models neglect the impact of wellbore growth / deepening on the downhole temperature, treating the wellbore). as having fixed dimensions. This leads to inaccurate temperature estimation, especially when drilling at a higher rate of penetration (ROP This paper presents a new modeling approach to overcome this shortcoming.

A coupled model of thermohydraulic flow in a growing wellbore was created based on a drift-flux model. It incorporates three key features. First, a dynamic, real-time meshing method appends new calculation cells to the bottomhole location as the well is deepened. Second, geometry and drilling fluid physical properties near the interfaces between drillstring sections and wellbore sections are updated dynamically as the drillstring moves forward. Finally, the drift-flux equation is adjusted to account for the well geometry changes associated with a moving drillstring.

The new model was validated using the open-source Utah FORGE field dataset and a previously validated model in a non-growing static wellbore. The DHT results from the new model converged to those from a well-calibrated model without wellbore growth when the rate of penetration (ROP) approached zero. Simulation results for a growing wellbore show that the DHT is generally higher compared to a static / non-growing wellbore and that this difference increases with higher ROP. The new model also provides new insights into the impact of the ROP relative to the pump rate on the DHT. When DHT estimation is needed for multiple wellbore sections, the new model only requires one set of input data to analyze the DHT at different well depths during the drilling operation. This is a major advantage in comparison to static-well models which require multiple input datasets, one for each wellbore section, with each input requiring carefully selected initial conditions to obtain realistic results.

This work provides a new modeling tool, validated against a static-wellbore solver and field data, to estimate and manage the DHT in higher-temperature oil, gas and geothermal wells. The model, which has the potential to run in real time and thereby digitally twin the drilling operation, may contribute to preventing premature temperature-related failures of bits and downhole tools while drilling future wells in high-temperature environments.
A New Polymer Based Multifunctional Fracturing Fluid With Enhanced Proppant Transport Capability
Authors: Lin Genyao , Huang Jiangshui , Song Lulu , Richardi Bryant , Li Jianshen , Liu Fuchen , Lin Lijun
Published: October 2023

Multifunctional fracturing fluid is desirable in the oil and gas industry as it can reduce operational complexity and footprints during hydraulic fracturing. Traditional slickwater fracturing fluid has limited proppant transport capability and lacks other functionalities. Most reported publications and practices on proppant transport enhancement were largely realized via increasing the viscosity of the fracturing fluid by using high viscosity friction reducer (HVFR) or simply increasing dosages. Recent multifunctional fracturing fluid research has also demonstrated that the combination of HVFR with nano-emulsion can provide the effect of spontaneous imbibition oil displacement to improve oil recovery (IOR) and thus achieving the goal of combining both hydraulic fracturing and IOR. While fracturing fluid with high viscosity has been used to increase its proppant carrying capability, it comes with the compromise of reduced fracturing length, fewer secondary fractures as well as requiring multiple additives to achieve multifunctionalities.

In response to the industrial needs of multifunctional fracturing fluids with reduced operational footprints, we report a multifunctional fracturing fluid based on a novel single polymer system containing oil-displacement surfactant. The new polymer based fracturing fluid was characterized in terms of friction reduction, proppant settling, rheological properties and Amott cell spontaneous imbibition tests.

The flow loop results showed that the new polymer system based fracturing fluid can achieve friction reduction of more than 70% in both fresh water and 55K brine. Remarkably, the new fracturing fluid at 0.4wt% can suspend the 20-40 mesh ceramic proppant for an extended period without apparent settling. Breaker studies and rheological properties of the fluid were performed using traditional breaker ammonium persulfate at various dosages. The spontaneous imbibition test on the broken fluid showed a significant increase in oil recovery as compared to the control sample.

The results showed that the novel multifunctional fracturing fluid can be used as a traditional friction reducer at low dosages with over 70% friction reduction; while at high dosages, the fracturing fluid exhibits superior proppant carrying capability due to the formation of three-dimensional structures facilitated by hydrophobic association. Additionally, the multifunctional fracturing fluid can be easily broken by traditional peroxide breaker to release the oil displacement surfactant to enhance oil recovery as demonstrated by the spontaneous imbibition test. The presented multifunctional fluid can reduce the number of additives needed in the field and its enhanced proppant transport capability can result in less freshwater usage and less environmental impact.
Evaluation and Study of Dissolvable Frac Plugs on Horizontal Well Fracturing, Plug and Perf Completions
Authors: Almulhim Bassam Khalid , Ashby Scott , Alobaid Hashem , Alyousef Abdulmuin
Published: October 2023

The paper focuses on the use of dissolvable plugs in plug and perf completions, which allows the frac operations to be carried out, isolating between stages, and when the job is complete, the well can be flowed-back immediately. The need to mill out as with conventional plug is eliminated as each plug is disintegrated to a fine powder, not generating any flow restriction. Risks associated with milling and potential casing damage is eliminated, resulting in safer operations and operational savings. It also reduces the possibility of filling the open fractures with debris or chips from the milling process, minimizing damage to the fracture permeability. The focus of this paper will be on the dissolvable plug used to isolate the stages, which holds pressure for enough amount of time accordingly to the well operations. The design of these plugs also allows them to be used in long horizontal or extended reach wells without concern regarding the mechanical limitations of the coiled tubing during milling phase. The plug performance supports increasing the number of stages in these wells which resulting in higher well productivity while minimizing the well integrity aspect as the milling operation is not required.
Real-Time 3D Imaging of Neat, and Viscosified CO2 in Displacement of Brine-Saturated Porous Media
Authors: Ding Boxin , Kantzas Apostolos , Firoozabadi Abbas
Published: October 2023

CO2 storage in saline aquifers may contribute to a 95% share in preventing emissions to the atmosphere. The process is inefficient due to low CO2 viscosity at the subsurface conditions. Most of the injected CO2 will spread quickly at the formation top and increase the probability of leakage. This work is aimed to demonstrate improved CO2 storage in saline aquifers by effective viscosification/thickening of the sc-CO2 at very low concentrations of engineered polymers and by slug injection. We also present results from X-ray CT imaging to advance the understanding of two-phase CO2-brine flow in porous media and firmly establish the transport mechanisms.

X-ray CT imaging of displacement experiments is conducted to quantify the in-situ sc-CO2 saturation spatiotemporally in brine-saturated Berea sandstone cores. In neat CO2 injection, gravity override and viscous fingering result in early breakthrough and low sweep efficiency. Cumulative brine production is approximately 30% (from fraction collector) and 35% (from X-ray CT imaging) at 2 PVI. The difference between the two is attributed to the solubility of the produced water in the produced CO2 at atmospheric pressure which has been neglected in the past. We show that when the forgotten effect is accounted for, there is a good agreement between direct measurements and in-situ saturation results.

In the past, we have demonstrated that effectiveness of an oligomer of poly(1-decene) in displacement of brine by CO2 at a concentration of 1.5 wt.%. In this work, we show that the same polymer is effective at low concentration of 0.6 wt.%. The oligomer slows the breakthrough by 1.6 times and improves the brine production by 35% in horizontal orientation. Such a large effect is thought to be from the increase of the interfacial elasticity, based on the X-ray CT imaging of displacement experiments. We also show that there is no need for continuous injection of the oligomer. A slug of 0.3 PVI viscosified CO2 followed by neat CO2 injection has the same effectiveness as the continuous injection of the neat CO2. In this work, we also demonstrate the effectiveness of an engineered new molecule at 0.3 wt.% that may increase residual trapping by about 30%. The new molecule has much higher effectiveness than our recent molecule. The combination of mobility control and residual brine saturation reduction is expected to improve the CO2 storage in saline aquifers by effective viscosificaiton with low concentrations of oligomers.
The Traditional Drilling Optimization Conceptually Deadlocked for Realtime Well Engineering: An Alternate Solution
Authors: Samuel Robello
Published: October 2023

The industry has seen several methods of drilling optimization over the years. One of optimization's advantages—namely, its innate mathematical rigor—can also be seen as a disadvantage because of the downhole unknown and uncertain conditions. As a result, the traditional mathematical based models suffer from the optimum drilling parameters being inaccurate and more specifically in a non-convergence deadlock in real time and render useless and may lead to infeasibility when used in real time. To address the issue, in this paper, an opto-satisficed time-optimal batch methodology is proposed that brackets the feasible solution space using various engineering models.

The analysis results have shown that the convergence optimal bound space was very quick in obtaining an optimal drilling parameter in realtime and the predictability in the test wells has shown the best solution results under uncertainty. It has also been found that the results provide reasonable threshold values when more data is used as the well is drilled. As long as the driller stays within the operational region, the results have shown that the operating parameters are satisfying and good enough for the desirable outcome. In other words, a near-normal engineering solution is achieved. It has been found that the methodology can adapt the operating condition by combining the theoretical engineering models with the realtime measurements. The actual results from drilling several wells are used to illustrate the efficiency of this method over the traditional drilling optimization algorithms. Comprehensive results are presented in the paper with various examples with derived operational parameters when the well is drilled in realtime that satisfy the drilling engineers as well.
A Fast and Reliable Network Solver Using Numerical Proxy for Reservoir Simulation
Authors: Yang Yahan , Davidson Jeffrey E. , Verma Kaushal
Published: October 2023

Reliable and efficient modeling of subsea production systems is critical for predicting performance of offshore reservoirs. Iterative numerical procedures are typically required if the production system includes flow networks where wells may compete and interact with each other. The network problem can become challenging since production constraints, hydraulic flow stability, and other issues need also to be considered when solving for numerical values of pressure and rates.

In this work, a new technique, called stability proxy, for solving flow network problems in reservoir simulation has been developed by generalizing the concept of inflow performance relationship (IPR). IPR is traditionally used for representing the quantitative relationship between flow rate and bottom-hole pressure (BHP) or tubing head pressure (WHP) of a well. With stability proxy, IPR-like relationships are constructed for the entire production network, including wells and facilities downstream to wellheads. This approach handles production constraints and hydraulic stability and employs approximation techniques for computational efficiency.

Stability proxy offers several advantages compared to traditional techniques for solving flow network problems. First, stability proxy method determines pressure/rate operating ranges for wells and locations downstream in a flow network. Given a pressure or rate boundary condition, the computational procedure identifies wells that are open to production and wells which cannot flow due to lack of pressure support, flow instability, and other reasons. After well state is determined, rates and pressure anywhere in the flow network can be easily determined from the stability proxy dataset. In contrast, traditional methods for solving the facility network problem start computations assuming wells are open and often require good initial guess to converge successfully. The stability proxy method does not require initial guess, eliminating numerical artifacts from the solution process. Second, performance of traditional iterative approach often degrades when wells are operating near the stability limit, and multiple network calls are often required to ensure that well production allocation is consistent with the network model downstream to wells. With the proxy algorithm, computational efficiency is significantly improved since proxies can be reused in many situations without compromising accuracy. Using stability proxy results, a semi-analytical method is derived for obtaining derivatives of production rates with respect to flow control variables, which provides a fast and convenient tool for quantifying well interference. Effective gas-oil ratio (GOR) and water-cut (WCUT) accounting for well interference are defined for flow networks based on the derivative results. Tests show that effective GOR and WCUT can be used as a more realistic basis for production allocation in field management.
Integrated Multiphase Flow Modeling for Downhole Pressure Predictions
Authors: Alkhezzi A. , Fan Y.
Published: October 2023

This work presents a new integrated multiphase flow model for downhole pressure predictions. The aim of the model is to produce relatively more accurate downhole pressure predictions under wide flowing conditions while maintaining a simple form. As a component of the integrated model, an improved two-fluid model for segregated flow is proposed. Results of the two-fluid segregated model are compared with five state-of-the-art existing models, while results of the integrated model are compared with three.

The proposed integrated model incorporates the state-of-the-art onset of liquid loading predictive model. It classifies the flow into two major categories based on the onset of liquid loading, that are modeled by two different approaches respectively. If liquid loading occurs, the model uses a sophisticated drift-flux model which proved to be simple and relatively accurate when dealing with high liquid holdup. On the other hand, if liquid loading does not occur, an improved two-fluid segregated flow model will be used. The proposed two-fluid model was developed by improving the modeling of wetted perimeters and the liquid wall shear stress.

The proposed new two-fluid model for segregated flow outperformed five other existing state-of-the-art models in predicting the liquid holdup and pressure gradient of 11 experimental datasets from the literature. The datasets range widely in pipe diameter, inclination angle, gas density, and flowing conditions. The model succeeds in capturing the effects of inclination angle, pressure or gas density, and liquid and gas superficial velocities on liquid holdup and pressure gradient. The new model eliminates the need of changing interfacial friction factor correlations when the flowing condition variates, significantly reducing the uncertainties and complexities associated with closure relationship selection and alteration. Moreover, the new integrated model outperformed the other multiphase flow models in predicting the downhole pressure of 313 field data points. When dealing with wells that have both segregated and intermittent flows, the new model produces outstanding results compared to other existing state-of-the-art models. In addition, it is capable of predicting the location and amount of liquid loading in a well, which will benefit the design and optimization of artificial lift processes.
Diammonium Hydrogen Phosphate Treatment for Sustaining Long-Term Acid Fracture Conductivity of Chalk Formations
Authors: Samarkin Yevgeniy , Aljawad Murtada Saleh , Solling Theis Ivan , Amao Abduljamiu Olalekan , AlTammar Murtadha J. , Alruwaili Khalid M.
Published: October 2023

The reactive acid, injected into the formation during acid fracturing operations, etches the surfaces of the fracture, generating asperities that keep the fracture conductive. However, the stresses acting on the fracture tend to close it, destroying the asperities. Asperities' destruction is especially severe in soft carbonate formations such as chalk. This work focuses on improving the long-term acid fracture conductivity sustenance by hardening the chalk rocks through chemical treatment.

Diammonium Hydrogen Phosphate (DAP) is applied to harden chalk slabs treated with 10% HCl acid in this work. Treated slabs are inserted in the API conductivity device that allows for measuring the conductivity of the fracture. The conductivity of the fracture treated by DAP after acid injection is measured at different stresses and compared with the conductivity of the acidized fracture with no DAP treatment. Furthermore, the additional analysis is conducted to observe the changes in the roughness and hardness of the samples before and after treatments.

The results demonstrated that the hardness of the chalk samples was decreased by 30 - 40% after acidizing. However, the subsequent treatment of the acidized samples with the DAP solution restored their original hardness. Moreover, the hardened samples were more deformation-resistant to the applied stresses based on Linear Variable Differential Transformers'(LVDT) measurements. The conductivity of the DAP-treated fracture decreased less abruptly with applied stresses (up to 2,500 psi) compared to the acidized but untreated fracture. As a result, the ultimate conductivity of a DAP-treated fracture was 60 md-ft, which was significantly higher than the conductivity of the untreated fracture that constituted 8 mdft. Additional long-term conductivity experiments were conducted over time (6 days) while applying the fixed stress. These experiments have shown that the decline in the conductivity of treated fracture is less severe compared to untreated fracture. It was noted that the plateau value of long-term fracture conductivity for the treated samples was significantly higher than for the untreated case.

This work presents a novel approach to sustaining acid fracture conductivity in soft chalk formations through chemical treatment with a DAP solution. This approach is validated through the API conductivity experiments that mimic the behavior of a fracture at reservoir conditions. The positive results obtained from this research allow suggesting that the technique will have great potential if deployed in the actual field operations.
Barcoded NanoTags for Real-Time Tracing Cuttings in Mud Logging
Authors: Wang Wei , Chang Sehoon
Published: October 2023

Rock cuttings are often collected for lithology and petrophysical characterization during a drilling operation. The depth origin of the sampled cuttings could be determined by calculating the lag time required for the cuttings to travel from the bit to the surface, but traditional mud logging methods may give inaccuracies of ±10-20 feet in the depth correlation due to the shuffling and settling of cuttings as they travel with drilling fluid to the surface, especially for horizontal wells. Aramco researchers have developed a technology that pulse pumps a series of barcoded tags sequentially to label drill-cuttings when they are formed during drilling without adverse impact on the drilling operation in field, and field tests demonstrated that the depth-correlation uncertainty could significantly improve to about ±2 feet. However, this technology critically relies on the efficiencies of mud tracer materials and technology of rapid detection for real-time monitoring in mud logging. To enable the determination of cuttings at various depths and times, a number of mud tags are essentially needed. Towards achieving this goal, we have developed 6 series of novel tracer materials as mud tags and analytical methods for rapid, trace level detection of these tags. The new series of nano tracer materials (NanoTags) include CompTags, MagTags, PolyTags, FluorTags, CarbTags and FiberTags, in which unique compositions or optical properties as barcoded information are incorporated. The synthesized tracer materials have controllable compatibility with either water-based mud (WBM) or oil-based mud (OBM) and have been tested in simulated mud formulation and cutting samples. Stability tests demonstrated that the tracers are stable in simulated reservoir condition with high-salinity water and crude oil at elevated temperature (~95°C). These NanoTags in drilling muds can embedded into cuttings at a drilling bit and travel with the cuttings to surface, and then be identified by optical detection and other orthogonal analyses using various detection methods at nano-gram level in the cutting samples.
Prevent the Scale Deposition Inside Wellbore by Applying the Physics Without Using Chemicals
Authors: Ahmed Mohamed Ghareeb M.
Published: October 2023

The build-up of scale deposits inside well bores can have a significant impact on the efficiency of oil and gas well production and operations especially the artificially lifted oil wells. In this paper, we aimed to present very simple technique operator can apply to avoid scale deposition inside wellbore without using chemicals by applying only physical methods. This can be done by controlling wellhead parameters. Methods, Procedures,

Our methodology involved analyzing the flow dynamics, pressure and temperature conditions inside the wellbore, and by calculating the scale tendency of produced water formation, operator from wellhead implementing measures can control the formation of scale deposits. This can be achieved by changing the flow dynamic inside the wellbore at the depth where scale start to deposit.

The results showed a significant prevention in the accumulation of scale deposits, leading to improved well production, operation and reduced maintenance costs without using any type of chemical treatment. Different real cases applications from the Egyptian oil fields will present.

The novelty of this paper lays in the application of physical methods to address the issue of scale deposition, which is a common challenge in some of the oil and gas industry. This approach offers a cost-effective, operation efficiency and environmentally friendly solution for mitigating the impact of scale deposition in well bores.
Open Hole Whipstock Technology Combines Cement Abandonment and Kick-Off in Single Trip
Authors: Emelander T.
Published: October 2023

In every basin around the world, planned or contingency open hole sidetrack operations are commonplace in drilling operations. In the recent year, there has been an evolution of the open hole whipstock systems to reduce sidetrack time/cost associated with kicking off from cement plugs. The most recent advancement for these systems combines kick-off operations in the same trip as setting whipstock and cementing the open hole below.

The whipstock systems that came to market in the recent unconventional shale era provided the industry a much-needed low risk/efficient option in wells where cement abandonment was required or desired, but kick-off from the whipstock was completed on the following trip. The most recent advancement in open hole whipstock technology utilizes the same concave, anchors, and abandonment methods but is deployed on a cutting structure rather than a running tool. The added ability to kick off in the same trip now further reduces sidetrack times when compared to cement plug or conventional whipstock kick-off operations.

This new open hole system has been installed in 18 wells in the United States (US), three different hole sizes, with 10 of these applications including cement operations to abandon and isolate the open hole below the whipstock. The original version of this technology was run on a crushed/insert carbide milling bottomhole assembly (BHA). The most recent cutting structure has been changed to polycrystalline diamond compact (PDC) cutters to decrease average kick-off times by around 50% and reduce the risk of a second trip in hard/abrasive formations. Two recent installs, including cement abandonment and PDC technology, highlight the success and benefits of this system. The first install was required because a radioactive source was left in the hole and the required deflection device (whipstock) could be used to sidetrack/continue well construction while pumping the required red cement and kicking off efficiently in one trip. Total well possession time for the operation including the wellbore preparation run was 64.5 hours. The second install was a planned pilot hole application with the kick-off being in the hard/abrasive shale. The local regulatory agency required the cement abandonment of lower exposed zones. Total well possession time for the operation including two wellbore preparation runs was 102 hours.

This paper shows that advancements in open hole whipstocks provide the industry with a reliable/efficient option for planned or contingency sidetracks. This sidetracking solution can be used in various applications worldwide to lower total time spent on the well construction process.
The Role of Fiber Properties s in LCM Design – A Numerical Approach
Authors: Henriques Cassian , Taleghani Arash Dahi
Published: October 2023

To combat the problem of lost circulation during drilling, lost circulation materials (LCM) have most commonly been added to the drilling fluid to seal the fractures and recover the rate of penetration (ROP). In recent years, fibers have become an attractive addition to many lost circulation treatments specifically due to their ability to overlap, intertwine and give rise to net-like structures within the fracture, that are able to effectively cause bridge-initiation and seal fractures. However, the behavior of fibers in particle-laden flow display multi-variate complexity due to the effects of multiple mechanisms – both particle and fluid related, that influence the fibers during flow. As a consequence, evaluating fiber LCMs in the lab in a detailed manner can be very cumbersome and tedious. To overcome this limitation, we developed a validated, Computational Fluid Dynamics coupled Discrete Element Method (CFD-DEM) model to simulate the fiber-laden fluid flow process in millimeter-wide fractures. The effect of fiber concentration, fracture roughness, and fiber stiffness on plugging capability is evaluated. It is found that, although fibers are known to create net-like structures that portray better fracture bridging than conventional LCMs, the bridging mechanism is affected by the bending stiffness of the fibers. We propose two new concepts for the bridging mechanisms of fibers and their effects on the plugging time and maximum plugging pressures for the LCM plugs. This study also attempts to better understand the effect of employing mixed blends of soft and stiff fibers on fracture plugging effectiveness by simulating mixed fibers of different soft-stiff compositions.
Assessing the Value of in-Well Fiber Optics Deployment in Pre-Salt Projects for Real-Time Reservoir Monitoring
Authors: Ribeiro P. M. , Gildin E. , Emerick A. A.
Published: October 2023

Brazilian pre-salt faces quite a few challenges for reservoir management given their complexity and uncertainty in fluid distribution and multiphase rate allocations along the wells. Real-time surveillance strategies and fluid control using intelligent completions are key to reduce uncertainty and optimize production. A central issue, however, is to determine the best strategy for real-time downhole monitoring systems deployment. Distributed acoustics and temperature measurements can be continuously acquired by fiber optics sensing (DAS and DTS, respectively), and thus can illuminate the determination of well information almost in real-time, but its value has not been quantified yet. Particularly, wet completions pose a challenge for the fiber optics application, requiring not only the investment in acquiring the hardware but also R&D to develop key missing components. In this paper we tackle this issue by providing a methodology for determining the value of distributed information for future deployments.

In this work, we apply a stochastic approach to estimate the value of information provided by in well fiber optics sensing. The study scenario considers representative characteristics of the main pre-salt carbonate reservoirs: thick, highly productive, and very heterogeneous, where the wells contain multizone intelligent completion. We compare data assimilation and optimization workflows applied to an ensemble of model realizations considering scenarios where only surface measurements are available (standard practice) and where the fiber optics provides the continuous downhole production/injection information. The impact of timing in the fiber optics deployment is also considered.

The rate allocation, especially in wells completed with intelligent completions and in fields performing water alternating gas injection, is essential to leverage decision making process and improve reservoir management. The cost of obtaining information from permanent sensors needs to be balanced against the expected benefit from improved reservoir performance, for example. Results show that the information provided by fiber optics sensing adds value by reducing the uncertainty and leading to an optimum well control closer to the optimum obtained with the reference (true) model. This value decreases as the information arrives later in time in a field development schedule.

Although the perception of the added value by fiber optic installations in this context is unquestionable, translating this value into numbers – which is essential for decision making – is not trivial task to achieve. The methodology proposed here enables the assessment of fiber optics sensing value of information applied to pre-salt reservoirs and is useful to guide the decision of acquiring or not this monitoring technology, particularly in the later development stages of a field.
A Data Analytics and Machine Learning Study on Site Screening of CO2 Geological Storage in Depleted Oil and Gas Reservoirs in the Gulf of Mexico
Authors: Leng J. , Wang H. , Hosseini S.
Published: October 2023

Carbon capture, utilization and sequestration (CCUS) is playing an important role in mitigating greenhouse gas emissions and reversing global warming. Finding suitable sequestration sites is a key stage for CCUS, however, numerous potential sites do not hold sufficient data for evaluation based on conventional criteria. This study presents a feasible and efficient composite-scoring system using data analytics method to provide feeding data for machine learning studies to assess the potential depleted oil/gas reservoirs for carbon storage with limited data available. BOEM database in Gulf of Mexico (GoM) is used to apply the scoring system as a case study. The paper first presents a description of the reservoir properties and geological properties in GoM; then, the paper introduces the analytics method that maximize values of the available data and generate the final composite score for machine learning models; finally, the paper applies unsupervised machine learning method to cluster the reservoirs based on the location and composite scores. The findings of this study present that the scoring system quantifies and generalizes different types of geological and petroleum data to be feasibly applied in machine learning studies. Besides, with the BOEM database, the study revealed the best scored reservoirs located along the Louisiana coastline with large capacity, good injectivity potential and great performance in safety and economy. The result is consistent with the previous multi-criteria screening studies.