bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on the Mechanism of Reversing Oil Displacement for Increasing the Production of Crude Oil in Low Permeability and Ultra-Low Permeability Oil Field
Authors: Guan Cuo , Li Yiqiang , Hu Wenrui , Ma Zilin
Published: October 2018

Conventional water flooding method becomes ineffective facing low and ultra-low permeability oilfields, and the recovery rate of the non water harvesting period is only about 20%. Most residual oil is trapped in the reservoir and cannot be recovered. The conversion of injection well into production ones is used on some scale at home and abroad as a technique of oilfield adjustment, stimulation and EOR. Yet, problems like the optimum converting time, microscopic stimulation mechanisms, etc., have not been clearly studied. The optimum time for reverse displacement can be acquired through forward and reverse displacement experiments of man-made cores with different permeability. Then, based on CT scanning technology an analysis is made of the processes of the forward displacement (till the converting time point) and the reverse displacement (till the end). According to the information of pores and water-oil distribution extracted from the CT graphs, water flooding characteristics and the change in residual oil distribution in different layers and at different displacement stages can be recognized. With the process of forward water injection, the residual oil in the core behave as types of discontinuous phases, including film flow, blob flow, slug flow, multi-pore flow, etc., the total volume fraction of which increases with the displacement continuing. During the reverse displacement, in contrast, the former dispersed residual oil gradually gathered in cluster that is comparatively more recognizable. Meanwhile, the amount of multi-pore flow ascend, which is most obvious. These factors made part of the residual oil better displaced. By above analysis, a reasonable microscopic explanation of the stimulation technology by converting injection wells into production ones. The article concisely and directly uncovered the microscopic mechanism of the reverse displacement to enhance oil recovery. Based on the study and taking other influential factors of development into account, instructions can be made on further EOR process of low and ultra-low permeability oilfield at lower costs and with higher efficiency, which is one of the top concerns for most low permeability oilfields.
Comparative Analysis of Different Well Patterns for Steam-Assisted Gravity Drainage
Authors: Fedorov Konstantin , Gilmanov Aleksandr , Shevelev Aleksandr
Published: October 2018

The paper is devoted to the development of SAGD simulation. New integrated model of the process is presented. This model predicts main technologic parameters of the process. Analytical and numerical analysis revealed significant features of the process. Critical steam injection rate was established that is needed for heat channel between injector and producer formation and process initiation. Consideration of stationary state of the process was the basis of maximum volume calculation of steam chamber. In the framework of proposed model, increase of sweep efficiency was considered. Approach for sweep improvement by transformation of well pattern is developed.
Integrated Engineering Approach for Drilling of the First Well in the Laptev Sea
Authors: Grishankov Vyacheslav , Galimkhanov Aydar , Bogdanov Sergey , Kharitonov Andrey , Tikhonov Evgeny , Khalilov Almaz , Berezin Alexander , Dubrovsky Maxim , Tsibulsky Mikhail , Suvorov Anton , Netichuk Igor
Published: October 2018

This document describes the integrated engineering approach and technical solution used to perform a construction project of the first wildcat well in Khatanga subsoil area of the Laptev Sea.

Because of the small scope of performed geological exploration works and the absence of any previously drilled wells within the target area, a low degree of geological knowledge existed for this project. The unique location of the license area eventually complicated the profile of the Centralno-Olginskaya 1PO wildcat well and the logistics on the peninsula, consequently affecting the planning and performance of the project.

In these conditions, RN-Shelf-Arktika OOO and Halliburton encountered a range of challenging tasks associated with high quality planning and safe performance of the expected work scope within the planned timeframes. Other challenges encountered included fulfilling all geological tasks required to reduce expenses and developing technological and organization solutions for the subsequent construction of wells and the discovery of a new oilfield in the Eastern Arctic.

Because of the low level of geological knowledge about the territory, the operator regularly assigned new geological tasks. These changes eventually resulted in a longer wellbore (5530 m, rather than 4200 m), increased scope of geological activities (a longer coring interval of 156 m, rather than 90 m), and well design changes (five casing strings, rather than four).

To ensure the fulfillment of the required tasks, the completion of the project was based on an integrated approach for the integrity of the proposed technological and organization solutions, high quality of planning, and risk management and application of advanced technologies. This approach ensured 100% fulfillment of the geological objectives within the established timeframes and helped to develop a map of lessons learned with recommendations to optimize time and costs in the construction of future wells at the new field. Because of the project remoteness and challenging climate conditions, the well construction cost is the key factor for efficient field development (Lebedeva et al. 2017).
Casing Design Optimization and Technologies Improvement of Horizontal Wells Construction on the Objects of PJSC LUKOIL in West Siberia
Authors: Bondarenko Leonid , Bakirov Daniyr , Kovalev Vitaly , Fattahov Marsel , Fatihov Vadim , Mazur Galim
Published: October 2018

The applying of the horizontal wells during 10-15 years is one of the key direction to improve the effectivity of the development traditional and new hydrocarbons’ fields.

The building of the horizontal wells usually performs in Cretaceous and late Jurassic systems by LLC «LUKOIL - West Siberia». The typical well's construction consists of the directional casing pipe (⌀323,9 mm); conductor (⌀244,5 mm); production casing (⌀177,8 mm) till the production back and liner string (⌀114,3 mm).

To optimize the construction of well due to long duration it was offered the optimized construction (3 stages) for horizontal well, which consists of directional casing pipe (⌀323,9 mm); conductor (⌀244,5 mm); production casing (⌀146 mm). (Fig. 1)

The drilling of horizontal wells with such construction was had high level of non-productive time in 1990. It was due to imperfection of technical and technological solutions, equipment and materials for drilling and completion, that was applied in past.

Because of the positive experience of the applying a new equipment types for bottom hole assembly, drilling fluids, survey technologies during the drilling, multi-stage fracturing, it was actual return to 3 stage horizontal well's construction because it was appeared the opportunity of the doing troubleproof works such as the waiting of cement consolidation around production casing, mounting and hydraulic proof test of the blow out equipment, changing the equipment to drill the liner string's interval, doing geological investigations and other operations. Besides the placement of full-opening casing (⌀146 mm) in horizontal interval allows more technological well's completion and to conduct re-multistage fracking, to investigate and to doing maintenance and isolation operations into the horizontal interval by the traditional technologies and equipment, and another operation into the interval of the productive strata.
New Magnetic Resonance Wireline Sensor for High-Resolution, Faster Logging, and Better Fluid Typing
Authors: Balliet Ronnel , Chen Songhua , Callirgos Manuel , Beard David , Li Lilong
Published: October 2018

A new wireline nuclear magnetic resonance (NMR) logging tool is capable of providing high-resolution logs at a logging speed that is twice that of the typical current MRIL® tool logging speeds. The new sensor features a stronger magnetic gradient to enhance the sensitivity of diffusion-based fluid typing; it also provides a much shorter inter-echo spacing (Te) to increase the data density per echo train. Consequently, the new sensor reduces the requirement of vertical averaging, which enhances the resolution of thin bed formation evaluation.

The new NMR sensor addresses industry requirements for reliable porosity, organic vs. intergranular porosity discrimination, and free vs. adsorbed fluid fractions in low porosity, heterogeneous unconventional reservoir evaluations. The paper discusses optimization aspects of the sensor, including antenna aperture, maximized packing density of frequency bandwidth, and multi-frequency short inter-echo spacings. The new NMR sensor is fully combinable with several nuclear, electromagnetic (EM), and acoustic logging instruments with a log vertical resolution that is comparable to that of wireline density logs.

Field tests from North American unconventional wells have demonstrated that only minimal stacking is needed to meet the 1 PU porosity repeatability and moderate stacking for reliable fluid typing, even in low porosity unconventional reservoirs. With an optimal number of frequencies used for unconventional reservoir applications, an advantage is realized from the total frequency bandwidth for optimal signal-to-noise ratio (SNR). The optimized SNR, in addition to the short Te, also improves the 1D T2 spectral and 2D map resolution and, consequently, free light hydrocarbon and organic pore fluids. Intergranular fluid signals are also resolved in several wells with porosity as low as ≤ 5 PU.
Challenges of Cementing Steam Injection Wells SAGD
Authors: Figilyantov Aleksandr , Chugaeva Olga , Garshina Olga , Okromelidze Gennadii
Published: October 2018

There are a number of high-viscosity oil fields around the world. A distinctive feature of such oil fields is a combination of two factors: high viscosity of oil and low temperature of its enclosing zone. Sometimes, the temperature of pay zone is comparable to the temperature of permafrost + 6 °C.

Thermal methods are used to intensify oil production in such oil fields. The main thermal method is the injection of steam into the formation. The temperature of the injected steam exceeds 200 ° C.

With using this technique of intensification, there is a challenge of keeping the integrity of the cement sheath behind the column, as the cementing conditions and operating conditions are incompatible. The curing of the cement stone occurs at a temperature about + 6 ° C. When the steam is injected, the cement sheath is heated to a temperature of + 195 ° C or more.

Thermal deformations of the columns occur: expansion, elongation, when high temperature is applied. To reduce the probability of steam breakdown due to thermal deformations of the column, thermo compensators are used. Moreover, to compensate for the thermal elongation, the shoe of filter pipe is set upper than bottom was drilled.
Successful Implementation of PMCD Technology in Kazakhstan
Authors: Amanbayev Yerlan , Karmanov Kanat
Published: October 2018

This paper describes the implementation of pressurized mud cap drilling (PMCD) technology, a variant of Managed Pressure Drilling (MPD), a successful technique frequently used on oil and gas fields in Kazakhstan. It also considers the planning phase, operational aspects, and results of drilling with the PMCD technique through challenging formations.

PMCD technology with a rotating control device (RCD) is a form of blind drilling, where the drilling fluid and formation cuttings are not transported to the surface. It is a non-conventional drilling technique designed to maintain annular wellbore pressure to prevent total loss of circulation. A sacrificial fluid (SAC) is injected through the drill string and light annular fluid is pumped down from the annulus to maintain borehole fill and prevent annular gas migration.

Wells in this field have encountered uncontrollable losses while drilling sections of the fractured carbonate. As a result, the application of PMCD technology to meet those challenges was an obvious choice in order to achieve target depth. Conventionally drilling of the 8-in. section resulted in fluid losses of more than 450 m3. Consequently, passing through these challenging zones the rig crew switched from conventional drilling to PMCD. The wells were then successfully drilled using the PMCD method, without any issues or well-control incidents, and planned TD was attained. By enabling the client to reach TD, Weatherford PMCD equipment transformed a previously undrillable well into a potentially valuable asset. This operation demonstrated that PMCD can be a viable drilling technique for future wells in the field.

PMCD technologies included reduced consumption of lost-circulation material (LCM) and reduced loss of mud to the formation, keeping the wells economically viable. The main objectives of these wells were to drill safely and efficiently to target depth (TD), to deliver the wells for production on schedule, reduce non-productive time (NPT), minimize the drilling risks and hazards, and optimize the drilling program.
Robust Uncertainty Quantification through Integration of Distributed Gauss-Newton Optimization with Gaussian Mixture Model and Parallelized Sampling Algorithms
Authors: Gao Guohua , Vink Jeroen C. , Chen Chaohui , Araujo Mariela , Ramirez Benjamin , Jennings Jim W. , Khamra Yaakoub El , Ita Joel
Published: October 2018

Uncertainty quantification of production forecasts is crucially important for business planning of hydrocarbon field developments. This is still a very challenging task, especially when subsurface uncertainties must be conditioned to production data. Many different approaches have been proposed, each with their strengths and weaknesses. In this work, we develop a robust uncertainty quantification workflow by seamless integration of a distributed Gauss-Newton (DGN) optimization method with Gaussian Mixture Model (GMM) and parallelized sampling algorithms. Results are compared with those obtained from other approaches.

Multiple local maximum-a-posteriori (MAP) estimates are located with the local-search DGN optimization method. A GMM is constructed to approximate the posterior probability density function, by fitting simulation results generated during the DGN minimization process. The traditional acceptance-rejection (AR) algorithm is parallelized and applied to improve the quality of GMM samples by rejecting unqualified samples. AR-GMM samples are independent, identically-distributed (i.i.d.) samples that can be directly used for uncertainty quantification of model parameters and production forecasts.

The proposed method is first validated with 1-D nonlinear synthetic problems having multiple MAP points. The AR-GMM samples are better than the original GMM samples. Then, it is tested with a synthetic history-matching problem using the SPE-1 reservoir model with 8 uncertain parameters. The proposed method generates conditional samples that are better than or equivalent to those generated by other methods, e.g., Markov chain Monte Carlo (MCMC) and global search DGN combined with the Randomized Maximum Likelihood (RML) approach, but have a much lower computational cost (by a factor of 5 to 100). Finally, it is applied to a real field reservoir model with synthetic data, having 235 uncertain parameters. A GMM with 27 Gaussian components is constructed to approximate the actual posterior PDF. 105 AR-GMM samples are accepted from the 1000 original GMM samples, and are used to quantify uncertainty of production forecasts. The proposed method is further validated by the fact that production forecasts for all AR-GMM samples are quite consistent with the production data observed after the history matching period.

The newly proposed approach for history matching and uncertainty quantification is quite efficient and robust. The DGN optimization method can efficiently identify multiple local MAP points in parallel. The GMM yields proposal candidates with sufficiently high acceptance ratios for the AR algorithm. Parallelization makes the AR algorithm much more efficient, which further enhances the efficiency of the integrated workflow.
Application of Peres Integral and Gladfelter Deconvolution to Unconventional Reservoirs - The Fractured Basement Case
Authors: Kubota Leonardo
Published: October 2018

This paper prescribes the application of Peres Integral Method (1989) and Gladfelter Deconvolution (1955) to the analysis of pressure-transient tests performed on fractured basement reservoirs. Such type of unconventional porous medium features a matrix that plays no role whatsoever, while a fracture network accounts for both conductivity and storability. Well tests in these unconventional reservoirs might be dominated by noise from wellbore storage effects, which drown out actual reservoir response. We show that the joint application of those methods can effectively purge variable-rate effects from the pressure data and, as a result, unveil reservoir-flow dynamics.
A Comprehensive Approach to Achieve Record Performance on the field named after V. N. Vinogradova
Authors: Yakunin Sergey , Kashin Evgeniy , Shtyfel Alexandr
Published: October 2018

JS "RITEK" since 2008 engaged in the development of deposits named after V. N. Vinogradova. Geological oil reserves are more than 100 million tons of oil and are hard to recover reserves. Target horizon is AS3. Development of the field. V. N. Vinogradov was carried out in several stages. The first stage took place at the end of 2008 and involved the well re-entry and re-testing of exploration wells of the field. The next stage was the drilling of horizontal wells with multi-stage hydraulic fracturing. The horizontal wells have the standard design: direction Ø324 mm – 50 m, conductor Ø245 mm – 800 m, production casing Ø178 – 2000 m and a liner with a long horizontal section Ø114 mm – 500 m. Over the past few years the development of the field, the length of the horizontal section increased from 500 m to 1600 m. For the successful drilling of wells with horizontal section of 1600 metres was conducted the work on optimization of equipment, technologies and parameters of drilling a conductor casing string and the shank. The article presents technical and technological solutions for drilling optimization.
Innovative Solution for Fluid Loss in Sub-Hydrostatic Wells During Workover Operation-Case Study from Kuwait.
Authors: Hassan Mohammad , Nour Ahmad , Al-Yaqout Thanyan , Agarwal Chakshu , AL-Mejmed Saad , AL-Saleh Fawaz , AL-Shammari Yousif , AL-Hazeem Fatema , AL-Khatrash Mouzah , Safar Emad , Hassan Ahmad
Published: October 2018

Fluid loss in sub-hydrostatic wells during overbalanced workover operation is a significant concern and includes three different challenges. The first challenge is the near wellbore damage due to the invasion of the completion fluid to the formation. The second challenge is the additional operating cost associated with both rig time spent to pump fluid into the well and stimulation treatment to restore the initial formation condition. The third challenge is maintaining a safe window of overbalance condition during the workover operation which is a major HSE & well integrity concern.

The outmoded technique to control losses is to use solids base fluid which could damage the formation if not properly removed after the treatment. Also, in some cases it requires an acid breaker to restore the original formation state. The acid treatment must be done before installing the pump in hole as the solid-fluid system can't be flow back through the artificial lift.

KOC keeps the safety window of the overbalance by pumping completion fluid (brine) into the well while killing operation. As a consequence, rig had to pump hundreds of bbls of brine into most of the depleted reservoirs which in most of the cases causes sever wellbore/reservoir damage (major concern) leading to delay in Production and increase in operation cost associated with rig time and completion fluid cost.

Customised Salt Pill system is a unique solution for such challenge, and it had been proved trouble-free globally by sealing the face of the formation during the killing operation. Recently the salt pill system was deisgned and deployed in a well in one of KOC brown fields, the job magnificently compiled with KOC success criteria safely. Moreover, the fluid level was static in the well during the entire workover operation. With the successful flow back for the well after ESP installation, demonstrated no wellbore damage with salt pill even without requiring any breaker nor acid.

The application of Salt Pill was successful and it lead to saving of approximately two days of rig time and Early Production from the well without damaging the reservoir with the invasion of completion fluid. This innovative solution has opened the way forward for KOC to implement same technology in other sub-hydrostatic wells.
Fit-for-Purpose Water Treatment in Permian Shale – Field Data, Lab Data and Comprehensive Overview
Authors: Walsh John , Sharma Ramesh
Published: October 2018

Sourcing water for hydraulic fracturing and disposing of produced water are well-known constraints and significant cost items in the development of shale formations in the Permian Basin. Utilizing a water life-cycle approach, some of the produced water can be treated and reused. However, there is usually more produced water than needed and some must be disposed, typically by injection into a disposal well. Whether the water is to be reused or disposaed, it must be treated to some extent. Given the volumes of water involved, treatment technology must be robust and inexpensive. This suggests that the selected technology should be tailored to the characteristics of the water and the quality requirements of the final purpose (reuse or disposal).

This paper starts with characterization of produced water from a few Permian shale fields and proceeds to the selection of appropriate conventional, robust and low cost treatment systems. Using this approach, fit-for-purpose treatment systems have been implemented in the field. Impairment problems with reuse and disposal of this treated produced water have decreased.
Effect of GOR on Gas Diffusivity in Reservoir Fluid Systems
Authors: Ratnakar Ram R. , Dindoruk Birol
Published: October 2018

Molecular diffusion plays a dominant role in various reservoir processes, especially in the absence of convective mixing. In general, gas diffusion in oils depend on several factors such as pressure, temperature, oil viscosity and gas-to-oil ratio (GOR). Out of these factors, GOR effects/live oil compositional changes on diffusivity is rare or not available in literature. The current work fills this gap and present the experimental observations on the effect of GOR on gas diffusivity in reservoir fluid systems.

Synthetic live oils were created by combining stock tank oil (STO) and methane in various ratios. Constant composition Expansion (CCE) experiments were performed with these oils to obtain their bubble points and liquid-densities in relation to GOR. Methane diffusivity in these oils were obtained from pressure-decay tests at high temperature/pressure conditions. The diffusion and solubility parameters were estimated from pressure-decay data using the diffusion model and integral-based linear regression presented in the previous works ([1]-[2]). The experimental and modeling methodology are presented here in sufficient detail to allow readers to replicate and evaluate the results.

In this work, we have experimentally investigated the effect of GOR on methane diffusivity in oils at high temperature/pressure conditions using pressure-decay tests. In particular, We present experimental data for bubble-points and liquid density of synthetic oils having various GOR-values. For the range of GOR's considered, these measurements show that the bubble-point pressure increases linearly with GOR.Late transient solution of the pressure-decay model was utilized to obtain diffusivity parameters by regressing against experimental data. It is found that as GOR-value increases (i.e. when oil becomes lighter), the diffusivity-value increases, which is in accordance with Stokes-Einstein relation.Most importantly, an empirical correlation is developed based on limited data set to describe the variation in diffusivity values with GOR. This can be very important when experimental data for the STO is available but not for the live oils. It can also be extremely useful in gas injection processes where amount of gas dissolved in the oil varies leading to variations in diffusivity as well.
An Experimental Study for the Using of Nanoparticle/VES Stabilized CO2 Foam to Improve the Sweep Efficiency in EOR Applications
Authors: Farid Ibrahim Ahmed , Nasr-El-Din Hisham
Published: October 2018

CO2 foam has been used to improve the sweep efficiency for EOR as a replacement for polymers to avoid potential formation damage. Foams degrade at high temperatures (>212°F), in high-salinity environments, and in contact with crude oil. The present work evaluates nanoparticles and viscoelastic surfactants (VES) to improve foam stability when these foams are used as EOR fluid.

This study investigates the stability of alpha olefin sulfonate (AOS) foam for different foam solutions in the presence of nanoparticles and viscosifiers (VES). To achieve this objective, foam stability tests were conducted at different temperatures up to 150°F. Foam stability was studied in a high-pressure view chamber (HPVC) to find the optimal. Single and dual-coreflood experiments were conducted at 150°F to investigate the divergent ability for the foam solutions on heterogonous sandstone formations. Boise and Berea sandstone cores with permeability contrast of 10-15 were saturated initially with a dead crude oil. The CO2 foam was injected with 80% quality as tertiary recovery mode. The oil recovery and the pressure drop across the core were measured for the different foam solutions.

Adding silica nanoparticles (0.1 wt%) of size 140 nm and viscoelastic cocamidopropyl betaine surfactant (cocobetaine VES) (0.4 wt%) to the AOS (0.5 wt%) solution improves foam stability. In contact with crude oil, unstable oil-in-water microemulsion generated inside the foam lamella that decreased foam stability. A weak foam was formed for AOS solution, but the foam stability increased by adding nanoparticles and VES. From the single coreflood experiments, the oil recovery from the conventional water flooding 47% of the original oil-in-place. AOS was not able to enhance the oil recovery. No more oil was recovered by AOS foam, however, extra oil was recovered in the presence of nanoparticles (19 %) and VES (26%). The dual-coreflood experiments revealed low sweep efficiency during the water flooding as a secondary recovery. Adding nanoparticles and VES to the AOS foam system increased the sweep efficiency and increased the oil recovery from the low permeability cores.

Nanoparticles and VES were able to improve the foam stability for AOS solution. Adding nanoparticles is highly recommended for EOR applications, particularly at high temperatures.
Pulsed Neutron Advances in Through-Casing Evaluation of Multilayered Reservoirs: Case Studies in the Mature Fields of the San Jorge Gulf Basin, Argentina
Authors: Maza Daniel , Oggier Fabian P. , Do Nascimento Carlos , Saldungaray Pablo J. , Zambrano Rafael , Mosse Laurent , Anci Pablo B. , Barrionuevo Pablo
Published: October 2018

An alternative technique to evaluate layered formations through casing in the Golfo San Jorge basin in Argentina is presented. The proposed methodology is based on pulsed neutron spectroscopy logs to assess the lithology and evaluate the hydrocarbon type and potential using resistivity-independent methods.

The basin's layered reservoirs present multiple challenges for resistivity-based methods, including low and variable formation water salinity, intricate pore systems affecting the rock electrical parameters, fine sediments with high irreducible water content suppressing the resistivity response, and high-resistivity tuffaceous sands not associated with hydrocarbons. In cased holes, simple correlations of resistivity and capture cross-section (sigma) or other techniques emulating openhole logs from basic pulsed neutron logs (PNL) can be used for interwell correlations, but are frequently inconclusive for assessing hydrocarbon potential. Our approach takes advantage of latest-generation PNL tools’ multiple measurements to reduce the uncertainty of water saturation assessment.

The proposed methodology was tested with two new-generation PNL tools, which feature high-resolution detectors that provide elemental concentrations for better understanding mineralogy including direct measurement of the carbon concentration for a reliable estimation of total organic carbon (TOC), which is directly associated with the oil volume in the pore space. The first tool was originally intended for openhole logging and has a single large detector for high-quality spectroscopy analysis. The second device is a multiple-detector slim PNL tool, which, besides the TOC and other spectroscopy outputs, also provides sigma and neutron porosity and measures a new property, the fast neutron cross section (FNXS), which is useful to detect and quantify gas. The presented case studies include examples of application with both tools in new wells and workovers. More than 20 sands, typically 2- to 5-m thick, interbedded with thick shales, were counted over the 1000- to 1500-m zone of interest, and all the data could be acquired in an acceptable time frame in spite the long intervals. The log data were complemented with the mud logging information and/or correlations from the static geological model. In all cases, we achieved good correlation between the zones with TOC, the static model, and well test results.

This experience illustrates the adaptation and application of new technologies to the development of mature fields where conventional openhole resistivity-based analysis is ambiguous. Future tasks include adjusting the technique for quantitative analysis and its use in deeper, more challenging, unconventional reservoirs in the basin.
Using Data Analytics to Assess the Impact of Technology Change on Production Forecasting
Authors: Male Frank , Aiken Chastity , Duncan Ian J.
Published: October 2018

The nature of well completions in the oil and gas industry continues to evolve. Although the effects of completions and spacing on initial production are well reported, how they affect ultimate recovery and terminal decline is not well understood. Over the last decade, drilling on multi-well pads has become prevalent, spacing between horizontal wells has decreased, and hydrofracture intensity has increased. These developments have decreased drilling and completion costs, while increasing initial well production. Yet, the impact of the timing, spacing, and intensity of fracturing on terminal decline rates and ultimate recovery has not been systematically investigated.

In this paper, Bakken well production profiles are used to evaluate the impact of differences in completion design on the nature of long-term production decline. To evaluate these effects, production for 12,000 Bakken wells were forecast using a physics-based approach. Using descriptive statistics and advanced visualization, terminal decline rate and ultimate recovery parameters are found to depend upon date of well completion, volumes of proppant and water injected, lateral length, and well spacing. We utilize a tree-based machine learning approach to test predictability of completion parameters on terminal decline rate and estimated ultimate recovery.

Our analyses show that pad drilling and increased hydrofracture intensity are apparently associated with small increases in initial production rates but have led to larger terminal decline rates. For example, in the Bakken, the terminal decline rate increases by upwards of ten percentage points for wells with modern completions in multi-well pads. Since production life is dependent upon terminal decline rates, spacing and completions effects must be accounted for in type curves for wells in multi-well pads.
Low Pressure - Condensate Recovery System LP-CRS. Creating Value Through Waste
Authors: Mohd Ismail Elmi , Rajah Benny , Suppiah Arul Jothy , Mat Ghani Shuhaimi
Published: October 2018

As a responsible and sustainable national oil company, the Malaysian Petroleum Management (MPM) of PETRONAS is committed to supporting the Paris Agreement via reduction of global Green House Gas (GHG) emissions by focusing on hydrocarbon flaring and venting optimization as a national agenda.

For fields with no means of gas evacuation or reinjection, complying with this national agenda would result in further capital investment for facility improvements or risk curtailment in production that would impact the oil revenue.

To realize the reduction of GHG footprint and generate value from condensate recovered from flaring and venting, a patented technology called ‘Low Pressure - Condensate Recovery System’ (LP-CRS) is applied. The LP-CRS is patented under NGL Tech Sdn Bhd and was jointly developed with Vestigo Petroleum Sdn Bhd under the guidance of Malaysia Petroleum Management (MPM) of PETRONAS.

A pilot LP-CRS deployed in an offshore Sarawak field in 2016 has proven to deliver significant reduction in GHG (CO2) emissions by more than 25% while recovering more than 100bbls/MMscf. These contributed to USD 7 million/year of additional value from a field with less than 30MMstb of recoverable reserves. The relatively simple operation and low maintenance of the modular LP-CRS, combined with its compact and lightweight build, makes the pilot technology attractive for replication in other offshore installations.

As part of future expansion plans, the LP-CRS has been earmarked for facilities that reinject gas for pressure maintenance and onshore gas terminals where complete gas processing facilities are not available.
Leakage Analysis and Structure Optimization of Sliding Vane Pump for Oil Recovery
Authors: Wang Shuolong , Wu Xiaodong , Han Guoqing , Ren Zebin , Tang Jingfei , Wang Hanlu
Published: October 2018

Sliding vane pump (SVP) is a new type of all-metal rotary hydraulic pump, which is applied to high-temperature thermal recovery wells possessing high pump efficiency. A leakage model based on the mechanical structure of SVP is presented that employs the principles of fluid dynamics. The leakage gaps of each pump chamber are divided into three parts: the gap between vane and vane slot, the gap between vane and the upper and lower valve plate, and the gap between vane tip and stator inner wall. According to the flow characteristics of fluid in each gap, the correlation equations are established from the perspective of shear and pressure difference respectively. Meanwhile, the optimum allocation of SVP is provided via comparing different structure parameters of pump on the basis of operating characteristic, including stator-rotor eccentricity, rotor-groove radius and vane parity. The significant new finding shows that the greater stator-rotor eccentricity, the greater delivery capacity of SVP, and the disequilibrium of the bearing increasing simultaneously. Therefore, the application of stator-rotor eccentricity in oil field should take into account multiple factors, such as well structure and production mode. Moreover, on the premise of meeting the requirement of pump weight and sand control, rotor-groove radius should be minimized to reduce the adverse effect on volume efficiency. Furthermore, the more vanes of SVP, the smaller period, and the greater average value of instantaneous flow rate. The flow pulsation of SVP with odd vane number is less than it with even vane number, and the recommended number of vanes is 5 to 8.
Phase Equilibrium of Hydrocarbons Confined in Nanopores from a Modified Peng-Robinson Equation of State
Authors: Cui Xiaona , Yang Erlong , Song Kaoping , Huang Jingwei , Killough John , Dong Chi , Liu Yikun , Wang Keliang
Published: October 2018

Phase behavior of hydrocarbons in confined nanopores is quite different from that of the bulk. In confined space, the high capillary pressure between vapor phase and liquid phase, and depressed critical properties under confinement will all affect the in-situ phase behavior. According to the theory of adsorption-induced structural phase transformation in nanopores, we modify the molar volume term of the Peng-Robinson equation of state (PR-EOS) by considering the reduced mole number of fluids caused by absorption to describe the phase behavior of fluids under confinement. Then capillary pressure is coupled with phase equilibrium equations, and the resulting system of nonlinear fugacity equations based on the modified PR-EOS is solved to present a comprehensive examination of the effect of capillary pressure and confinement on saturation pressures. Binary mixtures of methane with heavier hydrocarbons and a real reservoir fluid from the Eagle Ford confined at different pore sizes are considered. The effect of capillary pressure and confinement on the phase envelop shifts are compared.

The modified PR-EOS show that there exists a linear relationship between critical temperature shift and pore size reductions, a quadratic relationship between critical pressure shift and pore size reductions which are consistent with the experimental and molecular simulation results. The shift in the phase envelop of binary mixtures and Eagle Ford fluids show that both the capillary pressure and confinement decrease the bubble point pressures, while they oppositely influence dew point pressures. It is worthy to be noted that the effect of capillary pressure on phase envelop shifts will be suppressed when taking the critical point shifts caused by confinement into consideration. For Eagle Ford fluids, the effect of confinement on phase envelop shift is dominant compared with that of capillary pressure, and the capillary pressure cannot be overlooked when pore radius decreases to 50 nm. While the confinement begins to play an important role on the saturation pressures when pore radius decreases to 100 nm.

In addition, the methodology presented in this study can be extended to the phase equilibrium calculations of multiple pores since the modified PR-EOS can provide a consistent phase behavior description of fluid molecules over the whole range of pore sizes.
Oscillation Rheology of Dilute and Semi-Dilute Paraffin Wax Suspensions: A Novel Method to Study Wax Deposition Under Static and Quasi-Static Conditions
Authors: Smith Rashod , Miller Amanda , Mahmoudkhani Amir
Published: October 2018

As shale exploration has become more prevalent, producers are encountering more cases of shale oil with a high amount of paraffin content. With this introduction of paraffin wax, there are a number of challenges arise that include deposition of paraffin wax at well bore, in production tubings, chokes & valves, flow lines, separator and storage tanks which extend further down the pipelines to the refineries. With the growing demands in the global oil market for production optimization and cost reduction there is an increasing pressure for producer's and service companies to accelerate innovation in flow assurance and to deliver necessary best in class performance. While there have been great strides in treatment knowledge and method development in order to screen and optimize products under laboratory flow conditions, none are capable of simulating and measuring wax deposition under static or quasi-static conditions. These normally occur during annular flow, shut-in times, batch production and storage period. Our aim was to develop a simple, yet versatile technique to study deposition and control for dilute and semi dilute paraffin wax suspensions in condensates and model crudes comprising field paraffin waxes.
Small-Scale GTL, A Sustainable Alternative for Production of Transport Fuels in The U.S.
Authors: Ajagbe Oluwatobi , Moghanloo Rouzbeh Ghanbarnezahd
Published: October 2018

This paper examines the utilization of small-scale gas to liquid (GTL) plants for the production of transport fuels using abundant gas production from shale plays in the U.S. It is well-documented that GTL technology can be successfully implemented to convert natural gas to transport fuels. However, our literature is lacking an economic feasibility study of utilizing small-scale GTL plants as an additional stream of income for shale gas producers.

This paper describes two different practical cases detailing field constraints a shale gas producer should overcome to successfully generate additional income through GTL technology in a reasonable time frame. Economic metrics such as Net Present Value (NPV), Internal Rate of Return (IRR), Cost-to-Profit ratio and Payback Period were used to assess the success of GTL technology at each given business case.

For strategic decision making, sensitivity was built into the market drivers such as CAPEX, OPEX, interest rate, efficiency feedstock price, etc., and their level of influence on each economic performance benchmarks were analyzed. Monte Carlo simulation was used to carry out sensitivity analysis in each case to assess the mean and standard deviation of each economic performance metric when the range of possible values of the market drivers were put into consideration.

It is expected that the outcome of this research would guide shale gas producers and private investors when considering a GTL investment to monetize their assets in the United States and beyond.
Inhouse Design of Innovative Completion Equipment as an Alternative to Technology Transfer
Authors: Riabov Mikhail , Pustovalov Mikhail
Published: October 2018

In recent years import substitution and a technology transfer are ones of the hottest topics in oil and gas industry and relate to both economic and political situation. Most import substitution projects in Russia are carried out using methodologies of transfer of foreign technologies or the reverse engineering. In the context of this discussions technology transfer usually means the process of transferring technology from the foreign developer to domestic manufacturer. At the same time conventional oil & gas reserves are being depleted. The development of unconventional oil and gas reserves requires increasingly complex technologies that have not yet been developed by domestic companies. At the same time, foreign developers are not interested in the transfer of the latest, most effective technologies. Thus, if an import substitution is conducted only in a form of technology transfer, then the dependence of the Russian oil and gas industry on foreign technologies could not be overcome. And while geopolitical situation remains a difficult one, the technological gap between domestic and foreign industries will persist. And such gap will lead to a drop of oil and gas production in the Russian Federation.

This paper discusses an experience in realization of a different method of an import substitution, the in-house development of innovative technology. The challenges arising from implementation of such an approach are analyzed and lessons learned are described.
Water Source Identification and Inflow Profile Determination in Horizontal Wells after Multistage Hydraulic Fracturing Using Passive Location Method and Temperature Modelling
Authors: Aslanyan Irina , Minakhmetova Roza , Salmin Sergey , Trusov Alexander , Lutfullin Azat , Ganiev Bulat , Khabipov Rishat , Khabibrahmanov Azat , Yakupov Aidar , Morozov Pavel
Published: October 2018

One of the most effective oil production stimulation techniques in low permeability and heterogeneous reservoirs is multistage hydraulic fracturing. The multistage hydraulic fracturing technique has multiple engineering solutions dependent on the specifics of a particular target and its performance parameters. Hydraulic fracturing in a horizontal well involves a risk of communications with over- and underlying water-bearing formations via the fractures developing as a result of the hydraulic fracturing job. As a consequence, water cut in the well increases, negatively affecting the overall well performance. Another cause of a higher water cut could be a leak in the downhole completion.

To identify water sources in horizontal wells, modern logging techniques are applied. To enhance the informative value of a standard logging suite focused on inflow profile evaluation and integrity assessment in a multistage hydraulic fracturing well, SNL locator and acoustic flowmeter were added.

This paper discusses some cases of locating water sources in horizontal producers using new well logging and interpretation techniques. The information obtained as a result of well investigation was used to detect the water source and assess the multistage hydraulic fracturing job effectiveness. It was also recommended to perform workovers for the purpose of shutting off the water-producing zones.
A New Radial-Azimuth Thermal Anemometer for Determining the Direction and Velocity of Fluid Flow in the Wellbore
Authors: Valiullin Rim , Sharafutdinov Ramil , Fedotov Vladimir , Ramazanov Ayrat , Vakhitova Guzel , Kosmylin Denis
Published: October 2018

Measurement of fluid flow, especially for small values of flow rate, is important and, at the same time, a difficult task [1, 8-11]. The need for reliable measurement of this parameter is especially important for operating well logging. There are many flow measurement methods that are based on measuring the flow rate when the cross-sectional area is known. A wide-spread thermo-anemometer method was obtained in the study of producing wells. Its operation is based on the dependence of the body heat transfer on the flow velocity of its cooling fluid flow [3-5]. Thermal anemometers are used to detect inflow and uptake intervals; determination of leakage of the column under low-rate conditions, when mechanical flow-meter is ineffective. The sensors are reliable, compact, have low inertness. But with all the advantages, thermal anemometers have their own limitations: Only the first inflow interval is well defined, then the sensitivity decreases sharply;The change in ambient temperature can be perceived as a change in the composition or velocity of the fluid, which reduces the efficiency of determining the radial flow;The instrument's readings are strongly influenced by the axial flow of the liquid

In this regard, the development of more effective thermal anemometer sensor remains an urgent task.

In this case, the development of an azimuthally-distributed thermal anemometer of indirect heating is one of the possible ways [6,7].