bluuebunny/crossref_metadata_2025 huggingface dataset:
Completion Diagnostics Learnings from Shale Development Projects
Authors: Ramos Claudio R , Woodroof Robert A , Warren Mark N
Published: October 2018

Accelerating the learning curve in the development of the Vaca Muerta utilizing lessons learned in North American unconventional resource plays is the focus of this paper. Reducing completion costs while maintaining high productivity has become a key objective in the current low-price environment. Completion diagnostics have been demonstrated to optimize stimulation and completion parameters that have shaped successful field developments.

The paper reviews stimulation diagnostic data from wells completed in the Tuscaloosa Marine Shale, Eagle Ford, Wolfcamp and Niobrara shale formations. Case histories are presented in which proppant and fluid tracers were successfully employed in completion optimization processes. In the examples presented, diagnostic results were used to assess the stimulation of high productivity intervals within a target zone, evaluate various completion methods, and optimize stage and cluster spacing. The diagnostic data were compared with post-frac production rates in an effort to correlate completion changes with well performance. Results presented compare first, engineered perforations versus conventional geometrically spaced perforations to drive up effectiveness in cluster stimulation. Second, new chemistries, such as nanosurfactant, versus conventional chemistries to cut either completion cost or prove their profitability. Third, employing an effective choke management strategy to improve well productivity. Last, as in any stacked pay, determining fracture height growth in order to optimize well density, well spacing, field development and ultimately the recovery of the natural resources.

Completion effectiveness is shown to be improved by landing laterals in high productivity target intervals, increasing proppant coverage across the lateral by utilizing the most effective completion methods, optimizing cluster spacing and decreasing the number of stages to reduce completion costs while achieving comparable production rates. Cluster treatment efficiency (CTE), in particular, has become a critical metric when optimizing hydraulic fracturing treatment designs based on current and future well densities. It can be used to rationalize well performance as well as to identify possible candidates for a refrac program.

Using completion diagnostics, successful completion techniques were identified that led to production enhancements and cost reductions in prolific plays such as the Tuscaloosa Marine Shale, Eagle Ford, Wolfcamp and Niobrara.
Effects of Aqueous Solubility and Diffusion of Multi-Components on Shale Reservoir Recovery during CO2 EOR
Authors: Lee Ji Ho , Lee Kun Sang
Published: October 2018

The purpose of this study is to investigate effects of aqueous solubility and aqueous phase molecular diffusion of gaseous components when CO2 Huff and Puff process is applied into shale reservoirs. The gaseous components of CO2 and CH4 have solubility in water. In addition, flow of the CO2 and CH4 in shale reservoir is also affected by aqueous phase molecular diffusion phenemonon. Therefore, this study simulates CO2 Huff and Puff in shale gas-condensate and shale oil reservoirs considering the aqueous solubility and aqueous phase molecular diffusion of CO2 and CH4.

The aqueous solubility during CO2 Huff and Puff increases the CO2 storage capacity in shale reservoirs, but provides negligible change on production. However, aqueous phase diffusion phenomenon of CO2 increases contacting area between CO2 and oil in matrix and enhances the production of CO2 Huff and Puff in shale oil reservoir. To be significant in the simulations of CO2 Huff and Puff, considering mechanisms of aqueous solubility and aqueous phase molecular diffusion is necessary in shale reservoirs.
Determining Optimal Well Spacing in the Marcellus Shale: A Case Study Using an Integrated Workflow
Authors: Pankaj Piyush , Shukla Priyavrat , Kavousi Payam , Carr Timothy
Published: October 2018

Naturally fractured reservoirs such as the Marcellus shale require an integrated reservoir modeling approach to determine well spacing and well-to-well interference. The Marcellus Shale Energy and Environment Laboratory (MSEEL) is a joint project between universities, companies, and government to develop and test new completion technologies and acquire a robust understanding of the Marcellus shale. The study presented in this paper aims to reveal an approach to determine reservoir depletion with time through coupled geological modeling and geomechanical evaluation followed by completion and well performance history matching for a multiwell pad in the Marcellus shale.

The geomechanical model was prepared with interpreted vertical log data. A discrete natural fracture (DFN) model was created and used to determine the complexity of hydraulic fracture geometry simulated through complex fracture models on a two well pad. The microseismic data obtained during the hydraulic fracture simulations served as a constraining parameter for the hydraulic fracture footprint in these wells. Sensitivity to the DFN is realized by parametric variations of DFN properties to achieve a calibrated fracture geometry. Reservoir simulation and history matching the well production data confirmed the subsurface production response to the hydraulic fractures. Well spacing sensitivity was done to reveal the optimum distance that the wells need to be spaced to maximize recovery and number of wells per section.

Hydraulic fracture geometry was found to be a result of the calibration parameters, such as horizontal stress anisotropy, fracturing fluid leakoff, and the DFN. The availability of microseismic data and production history matching through integrated numerical simulation are therefore critical elements to bring unique representation of the subsurface reaction to the injected fracturing fluid. This approach can therefore be consistently applied to evaluate well spacing and interference in time for the subsequent wells completed in the Marcellus. With the current completion design and pumping treatments, the optimal well spacing of 990 ft was determined between the wells in this study. However, wells to be completed in the future needs to be modeled due to the heterogeneity in the reservoir properties to ensure that wells are not either underspaced to cause well production interference or overspaced to create upswept hydrocarbon reserves in the formation.

By adopting the key learnings and approach followed in this paper, operators can maximize subsurface understanding and will be able to place their wellbore in a nongeometric pattern based on reservoir heterogeneity to optimize well spacing and improve recovery.
From Wellbore to Seismic: An Integrated Approach for Geomechanical Characterizaiton of Naturally Fractured Reservoirs
Authors: Zhang Wenyu , Zhu Ding , Kim Jihoon
Published: October 2018

In unconventional plays, the performance of fractured wells is closely related to in-situ stress state and natural fracture distributions. The anisotropic geomechanical behavior of naturally fractured rock makes it difficult to appropriately evaluate the stress and geomechanical properties of the field. In this study, we present a wellbore-based, integrated geomechanics-seismic model that aims to improve the current stress field prediction and characterization of naturally fractured reservoirs, and ultimately, to optimize reservoir development.

The integrated model, starting from borehole-scale, uses a borehole stability model that considers the elastic anisotropy to provide the local stresses. Image log and other logging data are used to characterize natural fractures under local stress condition. A finite element based geomechanical model, which adopts anisotropic non-linear elasticity to best capture the physical behavior of fractured rock, is developed to estimate the current stress field at reservoir-scale, with wellbore stresses as constraints. The apertures of natural fractures in the reservoir are updated during the simulation. Seismic anisotropy caused by open fractures is then calculated and serves as another calibration method to improve identifying open natural fractures.

In this paper, a case study is presented. Given the estimated fracture spacing and aperture, the wellbore-based, integrated geomechanics-seismic model estimates a more homogenous maximum and minimum horizontal stress magnitude variations throughout the field comparing to an isotropic linear elastic geomechanics model. This also results in a narrower range for the horizontal stress ratio. The different results in the magnitudes of horizontal stresses will also cause difference in predicted fracture apertures, which results in changes in fracture permeability and porosity in coupled flow-geomechanics reservoir simulation. Eventually, for this case study, the seismic velocity anisotropy is predicted based on the simulated current stress condition.

Comparing to the conventional method for characterizing naturally fractured reservoirs, this integrated approach utilizing a wellbore-based, geomechanics-seismic model can estimate the stress field and fracture properties more rigorously. The improved results can be beneficial in aspects of well planning, hydraulic fracture design, and coupled reservoir simulation in unconventional plays.
Numerical Simulations of the Flow Past Crescent Cylinders for Flow Metering Purposes
Authors: Ahmed Yusuf , Ahmad Talha , Noui-Mehidi Mohamed Nabil
Published: October 2018

The present study is devoted to the flow peoperties of a vortex shedding system behind a bluff body that has a crescent cross-section, facing downstream of the flow. The investigation is conducted numerically using a lattice Boltzmann method. As a benchmark validation, the studied system was compared to the system of vortices formed behind the classical case of a circular cylinder for the same flow configuration and dynamic conditions, while varying the Reynolds number. The flow simulations have revealed that the crescent body affected substantially the shedding mechanism with remarkable differences when compared to the classical cylindrical case. There was a clear decrease in the shedding frequency with the crescent body that is beneficial when using this system as a metering tool.
High-Diffusivity Correction in Gas Interval Using 2D Magnetic Resonance
Authors: Oifoghe Stanley , Sy Rex , Okowi Victor
Published: October 2018

Due to a high noise-to-signal ratio, 10 of the 24 acquired magnetic resonance echo data logs from a field in the Niger Delta were excluded from the processing result. The reduction in the total number of echoes led to a high diffusivity, especially in the gas-bearing reservoir sand. High diffusivity caused some of the movable fluids to appear as irreducible bound water. The low hydrogen index of the gas also caused a low-permeability profile.

The effect of high diffusivity was very prominent in the Apparent Transverse Relaxation Time (T2app) spectrum, but the intrinsic transverse relaxation time (T2intrinsic) spectrum was unaffected. Consequently the, T2intrinsic spectrum was used to determine partial porosities and fractional fluid volumes. However, the total and effective porosities were not seriously impacted.

2D NMR (T2intrinsic – Diffusivity) maps were used to determine the partial porosities and fractional fluid volumes. These maps are produced by plotting diffusivity, D, against the Transverse Relaxation Time, T2. 2D NMR maps aid the discrimination of the magnetic resonance fractional volumes – clay-bound water (CBW), irreducible bound water (BVI) and movable volume (BVM). The maps can further be used for fluid-typing analysis.

The common processing result using T2app showed little or no permeability and little or no BVM in the gas interval, while the 2D NMR result showed an average permeability index of 3mD and an average movable fluid volume of 8pu. There was also very little BVI in this gas interval.

This paper effectively demonstrates the ability to use advanced magnetic resonance techniques to address issues related to high a noise-to-signal ratio, as well as minimal sensor failures. As presented, the paper clearly shows that we can get useable data from as high as 50% echo trains failure rate.

Though efforts are made to prevent signal failures and high noise-to-signal situations, there is a fix to such problems when they arise. Rather than re-log, the data can be savaged and the desired result achieved.
Waste Cooking Oil- A Potential Source of Raw Material for Localization of Green Products Development
Authors: Amanullah Md , Arfaj Mohammed K.
Published: October 2018

The oil and gas industry has a long standing initiative to develop and use the most environmental solutions in the exploration and recovery of oil and gas resources. As part of this continual effort, research is ongoing to create eco- friendly, virtually non-toxic and readily biodegradable base fluids, lubricants, emulsifiers to successfully complete drilling and completion requirements without causing any damage to the environment or other resources.

There is a significant volume of waste vegetable oil generated by the food and catering industry has no aromatic oil content, is virtually nontoxic and readily biodegradable and thus can be a potential source for the development of eco-friendly base fluids, lubricants, emulsifiers and spotting fluids to be in the forefront of best drilling practices This paper describes a set of newly developed green mud additives that have been synthesized using waste cooking oil generated by the food and catering industry. Recycling of the waste cooking oil not only provides a technical solution for the oil and gas industry, but also addresses the disposal problems of the food and catering industry.

Experimental results demonstrating the various applications of the newly developed green products indicate similar or better performance compared to the commercially available equivalent products used by the oil and gas industry. Hence, the newly developed products are viable alternatives for some of the imported non-ecofriendly or less eco-friendly oil-based products used for exploration and exploitation of oil and gas resources. Due to the replacement of equivalent imported products, these locally developed products will reduce the mud additive import cost significantly. On the other hand, due to the eco-friendly nature of the products, they will help explore and exploit oil and gas resources without any negative impact on other marine and terrestrial resources.
Effect of Polypropylene Fibers on Oil-Well Cement Properties at HPHT Condition
Authors: Ahmed Anas , Elkatatny Salaheldin , Gajbhiye Rahul , Rahman Muhammad Kalimur , Sarmah Pranjal , Yadav Prahlad
Published: October 2018

In deeper wells, high pressure and temperature post cementing operations put extreme stresses on the cement sheath and dramatically affect the cement integrity. So, the design of the cement slurry is very important to ensure the durability and long-term integrity of the cement sheath. The design should lead to a better zonal isolation and strengthen the bonding with the casing. Furthermore, it should help to shield the casing from corroding and unpredictable shock loads in deeper zones and sustain plugs to control the lost circulation in fractured and high permeability zones. Different additives were used to provide these functions such as; polymers, fibers, and bio-medicine in concrete history. Because of their large surface areas and small size, those particles are highly being used in the petroleum industry in the latest decades.

In this study, the usage of polypropylene fibers (PPF) is evaluated for oil well cement at high pressure and high temperature (HPHT) condition. The polypropylene fibers were added to the base cement in a different amount to evaluate its influence on enhancing the performance of cement.

The results obtained showed that adding polypropylene fiber to the base cement has a negligible effect on cement density, rheological properties, and free water. Using polypropylene fiber (0.75% base weight of cement (BWOC)) with the base cement reduced the thickening time by 75%; from 317 minutes to 78 minutes. The addition of Polypropylene fiber (0.5% BWOC) increased the compressive strength of class G cement by 17.8%. Polypropylene fiber can be used as an alternative material for silica floor in shallow wells. Polypropylene fiber has a significant effect on reducing the porosity and the permeability of the base cement.
New Hydrogen Sulfide Scavenger for Drilling Sour Horizontal and Multilateral Reservoirs
Authors: Elkatatny Salaheldin , Basfer Salem , Mahmoud Mohamed , Shawabkeh Reyad , Bahgat Mohamed
Published: October 2018

Hydrogen sulfide is naturally occurring gas that can be found in gas reservoirs, dissolved in hydrocarbon, water, or even liquid Sulphur. H2S can also be produced by microbiological processes, for example the reduction of sulfates by anaerobic bacteria such as sulfate reducing bacteria (SRBs). The existence of hydrogen sulfide even at low concentration yielded in localized corrosion and cause stress cracking. In addition, H2S causes damage to the pipes, valves and surface equipment.

Hydrogen sulfide is naturally occurring gas that can be found in gas reservoirs, dissolved in hydrocarbon, water, or even liquid Sulphur. H2S can also be produced by microbiological processes, for example the reduction of sulfates by anaerobic bacteria such as sulfate reducing bacteria (SRBs). The existence of hydrogen sulfide even at low concentration yielded in localized corrosion and cause stress cracking. In addition, H2S causes damage to the pipes, valves and surface equipment.

The objective of this study is to assess the using of copper nitrate as a catalyst for drilling fluids that can be used in drilling sour horizontal and multilaterals reservoirs. In addition, the effect of copper nitrate in rheological properties and the corrosion rate of the pipe will be evaluated.

The obtained results showed that adding copper nitrate with 1lb/bbl for the drilling fluid enhanced the rheological properties and H2S scavenging. The yield point/plastic viscosity ratio was increased by 20% without affecting the stress-strain behavior of the drilling fluid. The corrosion rate of the drilling fluid with the copper nitrate was very small (0.00060 lb/ft2 after 6 hrs) and (0.00084 lb/ft2 after 24 hrs) at 100°C. The standard corrosion (H2S + CO2, N2) test of the developed formulation showed that the corrosion rate was 0.00077 lb/ft2 after 6 hrs at 100°C. Breakeven experiments for base fluid, fluid with conventional Triazine scavenger, and the developed fluid showed that the drilling fluid with copper nitrate has three times the sorption capacity to H2S as compared to the drilling fluid with Triazine. The sorption capacity of the drilling fluid with copper nitrate is 5143 mg H2S/ml fluid, while that of both Bases and Base with Triazine fluids are 503 mg H2S/ml and 1666 mg H2S/ml, respectively.

The developed technique for H2S scavenging is very cheap and non-corrosive and will help the drilling engineer to drill multilateral and deep horizontal wells with safe and environmentally friendly method.
Designing Invert Emulsion Drilling Fluids for HTHP Conditions
Authors: Wagle Vikrant , Al-Yami Abdullah S. , AlSafran Ali
Published: October 2018

Good and optimal rheology is a primary requisite for a drilling fluid to achieve better hole-cleaning and barite sag resistance. Conventional thickeners like organophilic clay that provide rheology to invert emulsion fluids degrade with time and thereby fail to maintain sufficient rheology of the drilling fluid. Generally, excess amount of organophilic clay or low gravity solids (LGS) is added to the drilling fluid to enhance rheology. However, addition of excess amount of organoclay or low gravity solids not only increases the cost of drilling but also may severely affect other drilling fluid properties, which will require further treatment. In addition, addition of organoclay or low gravity solids increases the plastic viscosity, decreases the rate of penetration thereby ultimately increasing the cost of drilling. Thus, there was a need to develop a drilling fluid with optimal rheology sufficient to give good hole cleaning and barite sag resistance.

This paper describes the formulation of 70pcf, 90pcf and 120pcf organoclay-free invert emulsion drilling fluids formulated with the novel rheology modifier combination of RM1 and RM2. The invert emulsion drilling fluids were hot rolled at 250°F, 250°F and 350°F respectively. The paper also describes the static aging and contamination studies of 90pcf and 120pcf fluids at 250°F and 350°F respectively. Rheology of the 90pcf invert emulsion fluid was measured across high temperatures and pressures to observe their effects on the rheological properties of the fluid.

70pcf, 90pcf and 120pcf organoclay-free invert emulsion drilling fluids formulated with the novel rheology modifier combination of RM1 and RM2 showed optimal rheology and low HTHP fluid loss. Static aging studies of 90pcf IEFs at 250°F respectively showed that the fluids are sag-resistant with low top-oil separation. Contamination studies of 90pcf fluid showed that the contaminants have minimal effect on the rheology and filtration properties of the invert emulsion fluid. HTHP rheology of the 90pcf invert emulsion fluid shows consistent rheology across high temperatures and pressures. The paper thus demonstrates the superior performance of the rheology modifier combination to achieve good rheological and filtration properties.
Prediction of Cutting Concentration in Horizontal and Deviated Wells Using Support Vector Machine
Authors: Al-Azani Khaled , Elkatatny Salaheldin , Abdulraheem Abdulaziz , Mahmoud Mohamed , Ali Abdulwahab
Published: October 2018

Hole cleaning, or drilled-cutting transportation, is one of the main concern in the petroleum industry. This is due to the high impact of improper downhole cleaning during drilling operations. To illustrate, many drilling problems can happen because of inefficient cleaning of the wellbore. These problems may include premature bit wear, slow drilling rate (i.e. low ROP) and, in most severe cases, a stuck pipe which in some cases can lead to complete loss of the well. Moreover, measuring the cleaning efficiency using field or experimental measurements is highly costly and time-consuming which makes it a very complicated problem. Therefore, a lot of studies have been conducted to understand cutting transport efficiency in drilling operations. However, most of these studies are experimental and try to come up with the best measures including experimental models or empirical correlations. In this study, artificial intelligence techniques were used to estimate the cutting concentration in the wellbore.

The purpose of this study is to use Support Vector Machine (SVM) technique to indirectly measure the hole cleaning efficiency by predicting the cutting concentration in the wellbore from other operational parameters. Based on 116 experimental data points collected from the literature, the cutting concentration in the borehole was predicted from the properties of the mud itself such as the mud rheological properties (e.g. yield point and plastic viscosity) and mud density (mud weight) and other operational parameters during drilling including the drill pipe rotary speed (RPM), pipe eccentricity (i.e. the axial location of the drill pipe), hole inclination angle, the rate of penetration (ROP), flow rate (GPM), temperature and annular size.

The results obtained from SVM show the ability of this method to accurately predict the cutting concentration in the wellbore with an average absolute error (AAE) of less than 5% and a correlation coefficient (R) of more than 0.9. For this specific group of data, comparing the results obtained from this technique with a correlation presented in the literature shows that the SVM method provides a better prediction of cutting concentration and higher accuracy than that in the literature. Finally, the method developed in this study to predict the cutting concentration is based on continuously measured parameters during any drilling operation. Therefore, integration of the developed model into the drilling system will allow for real-time prediction of the concentration of the cuttings (i.e. the amount of cuttings present in the wellbore) and, hence, the cleaning efficiency during the drilling operation.
Prevention of Barite Sagging While Drilling High-Pressure High-Temperature (HPHT) Wells
Authors: Basfar Salem , Elkatatny Salaheldin , Mahmoud Mohamed , Kamal Muhammad Shahzad , Murtaza Mobeen , Stanitzek Theo
Published: October 2018

Barite sagging is one of the common issues while drilling high pressure-high temperature wells. This will cause variation in the mud weight in both vertical and deviated wells. Barite sagging can cause many problems such as; density variations, well-control problems, stuck pipe, downhole mud losses, and induced wellbore instability.

The objective of this study is to assess the effect of adding a new copolymer to the invert emulsion drilling fluid to prevent the sagging issue. Sag test was conducted under static conditions over a wide range of temperature (200°F to 350°F). Sag test was performed using vertical and decline (45° degree) aging cell. In addition, the effect of adding the new copolymer on the rheological properties and the electrical stability of the invert emulsion drilling fluid was evaluated.

The results obtained showed that adding 1 lbm/bbl of the new copolymer had no effect on drilling fluid density (14.5 ppg). The new copolymer slightly enhanced the electrical stability of the invert emulsion drilling mud. The new copolymer had a minor effect on the plastic viscosity, yield point, and gel strength. Adding 1 lbm/bbl of the copolymer prevent barite sagging at 350°F, where the sag factor was 0.55 before adding copolymer, and 0.503 after adding it. The storage modulus (G′) was increased by 40% after adding 1 lbm/bbl of the new copolymer confirming the sag test results. There was no effect of adding the new copolymer in the filtration loss and filter cake thickness.

The novelty of this work is the development of a new drilling fluid formulation that can be used in drilling HPHT wells without any sag issue. This development will help the drilling engineers to safely drill deep wells and maintain the drilling fluid integrity during the drilling operation. In general, this will reduce the overall cost of the drilling operation by reducing the non-productive time in solving many issues such as well control, loss of circulation, or pipe sticking.
Real Time Prediction of the Rheological Properties of Oil-Based Drilling Fluids Using Artificial Neural Networks
Authors: Al-Azani Khaled , Elkatatny Salaheldin , Abdulraheem Abdulaziz , Mahmoud Mohamed , Al-Shehri Dhafer
Published: October 2018

Continuous monitoring of the rheological properties of the drilling mud is essential so that any drilling operation can be completed more effectively and efficiently with the least problems. Mud rheological properties play a vital role in the in the efficiency of the drilling fluid to lift the cuttings from the wellbore. The mud rheological properties include the plastic viscosity, apparent viscosity, and the yield point. However, these properties are not measured continuously during the drilling process and they are only measured once or twice a day while other mud properties, such as the mud weight, the Marsh funnel viscosity, and solid content, are measured regularly and continuously. Therefore, it is valuable to come up with a relation that relates the mud rheological properties to these parameters. Many researchers tried to introduce models that allow for the prediction of the apparent viscosity from the Marsh funnel viscosity. However, these models have the deficiency that the prediction is with high errors. For the first time, the solid percent was used to predict the rheological properties of the oil-based drilling fluid based on the artificial neural network using actual field measurements.

The purpose of this study is to use the Artificial Neural Networks (ANN) Technique to develop a model that allows the prediction of the mud rheological properties such as the plastic viscosity, apparent viscosity, the rheometer readings at 600 and 300 rpm and the flow behavior index for oil-based mud from the mud weight, the Marsh funnel viscosity and solid content. The study is based on 400 data points collected from the field measurements of actual drilling fluid samples. The obtained results showed that the five developed models using ANN technique can be used to predict the rheological properties of oil- based drilling fluid with a high accuracy; the average absolute error was less than 5% and the correlation coefficient was higher than 90%. The developed technique is inexpensive with no additional required equipment. It will help the drilling engineers to calculate the equivalent circulation density, surge and swab pressures, and hole cleaning which are strong functions of the rheological parameters in a real time.

The method and approach used in this paper to predict and determine the unknown drilling fluid properties and trend out of accurately defined parameters is futuristic and progressive. The method is one step forward toward automating the drilling fluid system which is another step forward toward fully automating the drilling process overall.
Using Artificial Intelligence to Predict IPR for Vertical Oil Well in Solution Gas Derive Reservoirs: A New Approach
Authors: Basfar Salem , Baarimah Salem O. , Elkatany Salaheldin , AL-Ameri Wahbi , Zidan Khaled , AL-dogail Ala
Published: October 2018

Well Inflow Performance Relationship (IPR) has a wide range of applications in both applied and theoretical sciences, especially in the petroleum production engineering. An accurate prediction of well IPR is very important to determine the optimum production scheme, design production equipment, and artificial lift systems. For these reasons, there is a need for a quick and reliable method for predicting oil well IPR in solution gas drive reservoirs.

In this paper, back propagation network (BPN) and fuzzy logic (FL) techniques are used to predict oil well IPR in solution gas drive reservoirs. The models were developed using 207 data points collected from unpublished sources. Statistical analysis was performed to define the more reliable and accurate techniques to predict the IPR.

According to the results, the new fuzzy logic well IPR model outperformed the artificial neural networks (ANN) model and the most common empirical correlations. The average absolute error, least standard deviation and highest correlation coefficient were used to evaluate the models results. The proposed fuzzy logic well inflow performance relationship model achieved an average absolute error of 1.8 %, standard deviation of 2.9% and the correlation coefficient of 0.997.

The developed technique will help the production and reservoir engineers to better manage the production operation without the need for any additional equipment. It will also reduce the overall operating cost and increase the revenue.
Production Revival Using Hydraulic Lift Method for a Low Pressure Well: A Case Study
Authors: Rehman Abid Ur , Abdelbary Marwan , Abbasi Haris Shakeel
Published: October 2018

While the oil and gas sector is facing one of its most significant slumps, producers have moved their focus in optimizing production of their existing wells rather than drilling new wells. Artificial Lift Systems (ALS) have played a significant part in optimizing and enhancing the production of existing assets. The primary scope of ALS is to maximize productivity; however, there are many such systems applicable, the selection of the most suitable lift system plays a vital role in cost optimization of the well.

A primary type of ALS is hydraulic lift, which has been recently applied successfully in north Iraq. A special form of hydraulic lift is the jet pump. This technology has proved to be one of the best lift types for the operator in the region, with the unique concept of no moving parts inside the downhole pump, which has dramatically reduced downtime and the need to move a workover rig to the well site. A jet pump can be installed in a well using a variety of techniques, depending upon the well completion and can be customized easily depending upon downhole conditions. However, if one does not monitor the operation and working parameters continuously, the performance of a jet pump will be reduced as well conditions change.

A jet pump was optimized as a test project for a well which was not producing naturally. This study was based on a variety of operational conditions of the well, such as injection parameters, flow restrictions and paths, surface pumping unit power, nozzle throat combinations, vessel operating pressures, and the productivity of nearby wells to calculate the reservoir potential. The evaluation, analysis, and design of a jet pump for this well were carried out on Jet Pump Evaluation and Modeling Software (JEMS). The most suitable nozzle throat combination for this well was 10D, which was used successfully to lift production to approximately 2,000 bpd.

This study describes the process and gives the results for successfully reviving production in a well with hydraulic lift. It also depicts the improvements of the optimized input power for each well depending upon the design selected. In the end, a methodology towards the selection of the best design and operating parameters of the jet pump for the mentioned well is discussed. The installation, types, and operation of the jet pump system are discussed in detail for a proper understanding of the lift method.
Optimizing TVD Surveys in ERD Wells Minimizes Anticollision Risk
Authors: Al Hajri Hezam , Al Ghazzawi Ayman , Al-Yousef Fouad , Azher Mohammed , Madhi Adel Bin , Al-Mutairi Yousef
Published: October 2018

Typical well surveys are made once per stand, producing a 95-ft survey database; however, numerous things can take place in that 95 ft of pipe. Small changes in continuous inclination and azimuth lay hidden between traditional static survey stations. Processing these real-time measurements, in combination with traditional surveys, generates a definitive 10-ft survey list, resulting in an enhanced geometrical representation of the wellbore position. This enhanced wellbore positioning becomes increasingly significant in areas with high-anticollision risk. This type of survey processing was implemented in extended-reach drilling (ERD) projects in the Middle East. A comparison between the 95-ft surveys and the processed high-resolution surveys showed changes to 10 ft in the true vertical depth (TVD) measurements. Such shift in the TVD is important because it can result in having to revise planned trajectories to further minimize anticollision risk arising from the nearby TVD proximity with offset wells. This paper will present data to quantify the enhancement in TVD positioning using advanced survey processing in ERD projects in the Middle East, and its impact on minimizing anticollision risk.
A New Robust Approach for Hole Cleaning to Improve Rate of Penetration
Authors: Al Rubaii Mohammed Murif
Published: October 2018

Hole cleaning evaluation and prediction presents a challenge in drilling industry. The optimization of hole cleaning can reduce the down time during drilling operations. Good hole cleaning means high rate of penetration and less drilling problems. In this paper, a robust hole cleaning model is presented. It is based on monitoring and controlling simultaneously the carrying capacity index (CCI) and the cuttings concentration in the annulus (CCA) to ensure perfect hole cleaning. The cost of drilling can increase tremendously if not enough attention is paid to ensure proper hole cleaning. The knowledge of the size of cuttings, size of annulus, flow pattern, and down hole fluid properties cannot be determined with high level of accuracy using hole cleaning indicators such as transport ratio, hole cleaning ratio or transport index. Cutting concentration in annulus (CCA) alone cannot reveal the drilling mud properties, while the application of CCI alone will not help in optimizing ROP to the desired limit. The drilling parameters and mud rheological properties in certain hole sections were collected and analyzed first to determine the effect of mud properties and drilling parameters on hole cleaning and ROP performance. The data selected are from the same hole size, formation type and mud type. The relationship between mud rheological properties and CCI was then evaluated to determine how strong they are. This step helps determine the significance of mud rheological properties on estimating CCI. CCI and CCA were then simultaneously monitored and controlled to ensure proper hole cleaning leading to optimization of the Drilling operations and reduction in the drilling time. The data analysis demonstrated a strong link between rheological parameters and CCI. The approach was then validated by trial testing it in the field. The results showed that efficient hole cleaning level was achieved, which facilitated improvement of rate of penetration. It was used to drill in challenging hole sections and improved the well drilling performance by more than 55%, mitigated stuck pipe incidents, and eliminated wiper trips, reaming trips, and pumping of sweeps. The new approach or hole cleaning model showed the importance of combining CCI and CCA to optimize the drilling operations and reduce the time. This is the first time to combine the two techniques for hole cleaning optimization. The new hole cleaning model will help the drilling engineers drill a clean, stable hole in short time, and hence reduce the total cost of the drilling operations.
Correlating Dielectric Dispersion Data and Wettability Index of a Carbonate Rock
Authors: Al-Ofi Salah Mohammed , Dyshlyuk Evgeny , Sauerer Bastian , Valori Andrea , Ali Farhan , Abdallah Wael
Published: October 2018

Petrophysical models are used to estimate formation water saturation and salinity from dielectric dispersion data. These models are sensitive to other attributes of the formation such as wettability. Previous studies, analyzing different parameters of dielectric petrophysical models have shown how the dielectric dispersion is qualitatively influenced by rock wettability. Such analysis requires prior knowledge of the water saturation. To date, there is no direct method to quantify wettability from dielectric data.

In this work, we discriminate the effects of water saturation and wettability on dielectric dispersion data. We conditioned a 1.5-inch-diameter dolomite plug with solutions of different concentrations of stearic acid. In each set of experiments, we imbibed water into the sample and measured the dielectric dispersion in a frequency range of 10 MHz to 1 GHz using a reflection coaxial probe. This method enables us to obtain several dielectric measurements on a rock at defined wettability states and at different saturation levels. Then, the inverted dielectric interpretation answers such as water-phase tortuosity (MN) are analyzed for each dataset to distinguish their sensitivity to saturation and wettability. After each set of experiments, we measured the wettability index of the sample using US Bureau of Mines (USBM) and Nuclear Magnetic Resonance (NMR) methods and correlated it with dielectric inverted parameters.

Our findings show that the inverted interpretation parameters from dielectric data correlate well with the wettability index from USBM. These parameters include MN, the grain aspect ratio for the bimodal model, and the depolarization factors of water and oil-matrix of the textural model. We aged the sample into three wettability conditions: neutral-wet, strongly water-wet, and strongly oil-wet. For extreme wettability conditions, we observed a consistent trend of dielectric interpretation parameters with wettability during water flooding independent from saturation. For the neutral wettability case, the inverted dielectric parameters are constant up to a water saturation of about 50% and then starts to change gradually. For the strongly water-wet case, we observed a similar trend for depolarization factor as found in the literature, in which the nonwetting phase depolarization factor is close to the spherical geometry.

Our study illustrates how the inverted dielectric dispersion petrophysical parameters can correlate with well-established laboratory measurement of the wettability index, such as USBM method, for a specific core plug. This correlation can aid in estimating the wettability index directly from dielectric dispersion data for cores with similar rock textures. Different rock textures may impose different correlations, and further work is needed to establish a dielectric correlation for each rock type in a reservoir for application to downhole formation evaluation.
What is the Optimal Trajectory of Sidetrack Horizontal Well for Bypassing Obstacles in Cluster Wells?
Authors: Zhiyue Wang , Deli Gao , Jianjun Liu , Degao Hu , Wenrui Wu
Published: October 2018

Trajectory design of sidetrack horizontal well is faced with bypassing obstacles in cluster wells which makes the design process more complicated. The obstacle is assumed to be drilled trajectory sections such as vertical section and directional section, then they are described as a part of cylinder and annulus. Trajectory type for bypassing obstacle is classified based on geometrical relationship between tangent line of sidetrack point, tangent line of target point and axis of obstacle. The objective function is minimizing the total trajectory energy and the constraints include the safety distance to obstacle and the maximum build rate and maximum turn rate. Teaching-learning Cuckoo Search algorithm has been proposed to solve the established model. Case studies have been carried out according to different trajectory type, the results indicate that the proposed method can obtain sidetrack trajectory with minimum trajectory energy, in the meanwhile, the trajectory can avoid collision with obstacle and the wellbore curvatures are appropriate, the new method avoid trial calculation, it is also applicable to other types of sidetrack well trajectory for bypassing obstacles.
Petrophysics of Source Rock Reservoirs: A Complete Workflow
Authors: Eid Mahmoud , Abedeen Ainul , Kurri Janardhan
Published: October 2018

Source rock reservoirs have complex mineralogies and pore systems–their porosity varies from low to moderate, and their permeability varies from low to ultra-low and is in the nano-darcy range. The petrophysical evaluation of these complex reservoirs using only conventional logging tool (quad combo) data is highly complex and uncertain as a result of the tools’ limitation. Obtaining better and more certain petrophysical results for these reservoirs require integrating data from the conventional logging tool with the high-tech tools [elemental spectroscopy, nuclear magnetic resonance (NMR), dielectric, and spectral gamma ray].

It is challenging to calculate accurate porosity and water saturation values of source rock reservoirs using conventional log data. The presence of kerogen and complex mineralogies, such as conductive minerals, increases the difficulty. Because these petrophysical outputs are important for reserve estimates, any calculation error of these components directly affects the hydrocarbon in-place estimates. To address this issue, a new workflow has been developed to integrate data from conventional logging and high-tech tools.

This paper demonstrates a workflow designed to characterize source rock reservoirs by integrating data from conventional logging and high-tech tools. Additionally, this workflow helps provide accurate petrophysical outputs that are used later to estimate the correct hydrocarbon in place. This workflow was tested in multiple source rock reservoirs in the Middle East region. This workflow also provides mechanical properties (including Poisson’s ratio, Young’s modulus, closure pressure, and brittleness) of source rock reservoirs. The integration of rock mechanics and petrophysical results helps identify sweet spots that can be selected for fracturing operations.
Geomechanical Studies on CO2 Sequestrated Rocks in an Aqueous Saline Environment
Authors: Tariq Zeeshan , Abdulraheem Abdulazeez , Elkatatny Salaheldin , Mahmoud Mohamed , Muqtadir Arqam , Murtaza Mobeen
Published: October 2018

In a quest to reduce the greenhouse gasses, geologic sequestration of carbon dioxide (CO2) in an underground hydrocarbon rock formation or aquifer is one of the most promising alternative to reduce the amount of CO2 release in an open environment. However, long-term storage of CO2 effects the geomechanical and geochemical properties of the host rock. In carbonate aquifers, water dissolves the injected CO2 gas forming carbonic acid which has the tendency to dissolve calcium compounds present in the formation. The dissolution of calcium is particularly worrying since it contributes to the matrix of the rock. Thus, the mechanical properties of the rock are altered, which left unattended could result and in compaction of the formation and surface subsidence.

This paper aims to study the degradation of the petrophysical and mechanical properties of two types of rocks namely limestone and sandstone due to the storage of supercritical CO2 for desired amount of time. Supercritical CO2 has low viscosity but high density and has ability to store in large amount within the same space and with the high pumping efficiency. Two different carbonate rocks and one sandstone rock were exposed to a CO2-brine solution at a pressure of 1200 psi and at 120 °C for durations ranging from 10 to 120 days. The mechanical properties were then examined by both static and dynamic mechanical tests along with the routine core analysis (RCA).

Results showed that long term CO2 storage affected the mechanical, acoustic and petrophysical parameters of rocks examined in this study, viz., Khuff limestone, Berea Sandstone, and ordinary limestone. The duration of solubility time brine-CO2-rock has a considerable impact on the petrophysical and mechanical parameters of the rock samples. Outcomes of this study also shows that the rock mechanical and petrophysical properties significantly affected when CO2 store for the longer period of time. CO2, rock, and brine interaction is dependent on time consequently the rock mechanical and petrophysical parameters changes are also time dependent. The potential candidate found for geological sequestration of CO2 studied is limestone because of its minimal rock properties altered.