Integrated Hydraulic Fracturing and Well-Test Data Analytics using R

1. Abstract Various datasets are generated during hydraulic fracturing, flowback- and well-testing operations, which require consistent integration to lead to high-quality well performance interpretations. An automated digital workflow has been created to integrate and analyze the data in a consistent manner using the open-source programming language R. This paper describes the workflow, and it explains how it automatically generates well performance models and how it analyzes raw diagnostic fracture injection test (DFIT) data using numerical algorithms and Machine Learning. This workflow is successfully applied in a concession area located in the center of the Sultanate of Oman, where to date a total of 25+ tight gas wells are drilled, hydraulically fractured and well-tested. It resulted in an automated and standardized way of working, which enabled identifying trends leading to improved hydraulic fracturing and well-testing practices.

Main principles of the improved technique for the estimation of gas reserves in low-permeability Turonian sediments

The article describes the main principles of estimating volumetric parameters of gas onshore deposits in low-permeability reservoirs of the Turonian stage that were formed as a result of the long-term study of “supra-Cenomanian” sediments at the fields of Rosneft Oil Company PJSC, in particular, at the largest Kharampurskoye oil and gas condensate field. Based on a detailed analysis of the section, the authors formulated recommendations for optimal logging suite, well testing and analysis of the core taken from highly swellable clay rocks of the Kuznetsov formation.

Horizontal wellbore production profile evaluation by distributed fiber-optic temperature surveillance

The main goal of the paper is demonstration of permanent downhole long-term monitoring capabilities for oil and gas production profile along horizontal wellbore in case of natural flow. The informational basis of the results obtained is the data of long-term temperature and acoustic monitoring in the borehole using a distributed fiber-optic sensor (DTS + DAS). Materials and methods. At the same time, flowing bottom-hole pressure and surface rates were monitored at the well for rate transient analysis, as well as acoustic cross-well interference testing [1], based on the results of which “well-reservoir” system properties were evaluated, the cross-well reservoir properties of the were estimated, and the possibility of cross-well testing using downhole DTS-DAS equipment was justified. The research results made it possible to assess reliability of DTS-DAS long-term monitoring analysis results in case of multiphase inflow and multiphase wellbore content. In particular, DTS-DAS results was strongly affected by the phase segregation in the near-wellbore zone of the formation. Conclusions. In the process of study, the tasks of inflow profile for each fluid phase evaluation, as well as its changes during the well production, were solved. The reservoir intervals with dominantly gas production have been reliably revealed, and the distribution of production along the wellbore has been quantified for time periods at the start of production and after production stabilization.

Risk decreasing of water waste through spontaneous fracturing in injectors by integrated well-testing and production logging

Background. When creating an effective reservoir pressure maintenance system, unstable spontaneous hydraulic fractures can be created in injection wells. This can both negatively and positively affect hydrocarbon production. First, fracture improves reservoir connectivity, which increases injection efficiency. On the other hand, unstable fractures can cause behind-the-casing flows and unproductive injection into off-target layers or fingering. Goal. The paper is devoted to the analysis of well testing (PTA) and production logging (PLT) improvement for the diagnosis of unstable fractures in injection wells. Materials and methods. The analysis is based on the results of modeling the pressure in the reservoir system, describing the penetration reservoirs by an unrestricted conductivity unstable fracture. It is taken into account that the fracture can cross both the perforated formation and the thickness not penetrated by the perforation, and can grow with increasing overbalance. The modeling results made it possible both to assess the potential informative capabilities of well testing and to substantiate recommendations for the practical use of the obtained results. Conclusions. The proposed approaches to the technology of well testing and production logging and the interpretation of their results make it possible to estimate the additional thicknesses of the reservoirs connected by the spontaneous hydraulic fracturing to injection, the proportion of nonproductive injection in the total volume of the well. The research technology used by the authors is based on continuous measurements of pressure and flow rate during cyclic change of pressure and assessment of the effective transmissibility of the formation system at different heights of unstable fractures. The role of the PLT is to determine the effective production thickness of the reservoirs. When assessing the injectivity profile when penetrating the injector with the spontaneous hydraulic fracturing, the key role belongs to non-stationary temperature logging. In this case, it is necessary to take into account the specific features of temperature relaxation in the wellbore after the injection cycle, related to hydraulic fracturing, primarily the increase in the relaxation rate with increasing fracture length.

Penentuan Ekstrakurikuler Siswa Sesuai Minat Bakat dengan Case-Based Reasoning dan Certainty Factor

Extracurricular activities at MAN 1 Lamongan are still determined without any support from the system. Students are only given extracurricular information and can register according to the conditions if interested. This makes the extracurricular that students have chosen does not fully match their abilities. The result is a decrease in the number of members who are active in extracurricular activities due to loss of interest. A web-based system was developed to assist MAN 1 Lamongan in determining extracurricular according to interests and talents. Case-Based Reasoning (CBR) is the system framework and Certainty Factor (CF) is the algorithm for determining the certainty value. The result is that with test data of 68 students, the system recommends extracurricular well. Testing with Confusion Matrix obtained precision level of 96.03% (high), recall of 99.4% (high), accuracy of 95.76% (high)

A Comprehensive Model Integrating the Stress Sensitivity for Pressure Transient Behavior Study on the Two-Zone System for Offshore Loose Sandstone Reservoirs

Permeability changes in the weakly consolidated sandstone formation, caused by sand migration, has a serious impact on the interpretation of well testing and production prediction. In this article, a two-zone comprehensive model is presented to describe the changes in permeability by integrating the produced sand, stress sensitivity characteristics. In this model, inner zone is modeled as a higher permeability radial reservoir because of the sand migration, while the outer zone is considered as a lower permeability reservoir. Besides, non-Newtonian fluid flow characteristics are considered as threshold pressure gradient in this paper. As a result, this bi-zone comprehensive model is built. The analytical solution to this composite model can be obtained using Laplace transformation, orthogonal transformation, and then the bottomhole pressure in real space can be solved by Stehfest and perturbation inversion techniques. Based on the oilfield cases validated in the oilfield data from the produced sand horizontal well, the flow regimes analysis shows seven flow regimes can be divided in this bi-zone model considering stress sensitive. In addition, the proposed new model is validated by the compassion results of traditional method without the complex factors. Besides, the effect related parameters of stress sensitivity coefficient, skin factor, permeability ratio and sanding radius on the typical curves of well-testing are analyzed. This work introduces two-zone composite model to reflect the variations of permeability caused by the produced sand in the unconsolidated sandstone formation, which can produce great influence on pressure transient behavior. Besides, this paper can also provide a more accurate reference for reservoir engineers in well test interpretation of loose sandstone reservoirs.

Methodology of Effective Lateral Placement for Underbalanced Coiled Tubing Drilling Wells

This paper describes a methodology that has been developed to maximize lateral placement in productive reservoir intervals during underbalanced coiled tubing drilling (UBCTD) operations. UBCTD has emerged as an effective and economically viable development solution for exploiting reserves in mature gas reservoirs. In some cases, it can be a suitable solution to develop reserves in more geologically complex and heterogonous reservoirs over the conventional drilling and stimulation techniques. The methodology integrates big surface and subsurface data from multiple sources in multiple formats in real to near real-time that are normally acquired during UBCTD drilling operations. The multiple sources of data include subsurface geology, wellsite biosteering, reservoir influx, well testing and drilling, and can provide important information about the reservoirs encountered. With the aid of data analytics and an advanced visualization tool, the data is translated into in series of engineering plots that enable easier identification of productive intervals and more informed as well as efficient lateral placement decisions. This methodology has proven superior to the conventional instantaneous Productivity Index (PI) approach that is commonly used for UBCTD lateral placement. The methodology has been tested with good success in a number of recently drilled UBCTD wells in geologically complex depositional environments across carbonates and clastic reservoirs. Post flowback and pressure transient test analyses have shown significant improvement in the well deliver abilities and effective lateral lengths. Past performance from wells drilled using the PI method will be compared with wells drilled with this method.

Bringing New Levels of Automation and Flexibility to Well Testing Operations — Case Study

The oil industry has been perpetually examining well testing methods, with the goal of improving overall efficiency, ensuring data quality, and streamlining processes to achieve program objectives. Over the years, the aim of drillstem testing (DST) has remained mostly unchanged. However, operators want to meet the forecasted production investments of their fields, while improving operational efficiency and maintaining the highest level of operational standards, with safety and the environment being paramount. One of the solutions was developing a live, downhole, reservoir testing platform. The breakthrough consisted in introducing automation and real time monitoring to adjust the test program according to the actual reservoir response rather than blindly following a predefined test program, necessitating better operational flexibility. This platform is united by a wireless telemetry technology allowing an acoustic communication with downhole tools in real time. The automation of the data acquisition, downhole tools actuation and real time monitoring of the downhole operations, gives the operators the ability to perform well tests with reduced uncertainties, less human intervention and improved data quality. The early availability of reservoir knowledge enables operational efficiencies by meeting the test objectives earlier, thus reducing significantly the overall test period and the associated well testing costs. This paper describes the common well test objectives and challenges, the overall design of the wireless telemetry system, and automation of the job preparation and execution of the downhole operations that led to the successful completion of the well test campaign in very hostile condition, remote areas and restricted period. The use of the telemetry system in several well testing campaigns in different regions of the world, allowed to control critical downhole equipment and to acquire reservoir data transmittable to the clients office in town in real time. Various operation examples will be discussed to demonstrate how the automated data acquisition and downhole operations control has been used to optimize operations.

The Evolution of Green Completion in BP Khazzan Field

Well Testing is the single largest contributor of carbon emissions during well operations and the industry's aspiration to reduce carbon emissions inspired the bp Oman team to identify innovative ways to reduce emissions from activities in the Khazzan field. Khazzan is characterized by tight reservoirs which requires hydraulic fracturing to release gas from the rock. After fracturing, the wells are tested/cleaned-up by flowing the well fluids and flaring the produced gas and condensate to the atmosphere. The testing removes contaminants – proppant, frac fluid, hydrogen sulphide – that could damage the downstream Central Processing Facility (CPF). ‘Green Completion’ was one of the opportunities that was identified by the bp's Oman team to remove these contaminants in an environmentally friendly manner. A Green Completion is a zero flaring concept – hydrocarbons produced during well test operations are ‘cleaned’ and then routed to processing facilities for export rather than being flared. This concept has been successfully utilized in bp's onshore US operations for over a decade. The team leveraged the experience from the USA, applying this technology to suit the conditions in Oman, but it was not simple nor straight forward. In the last two years, this process has been modified and reinvented for the operations in Oman as the company seeks to strategically reduce its global carbon footprint. In first half of 2018, the bp Wells team initiated a pilot project with the objective of developing Green Completion capability in the Khazzan field. This was the start of the journey to demonstrate bp's commitment to reducing greenhouse gas (CHG) emissions in a sustainable manner. Furthermore, bp's collaborative cross-functional aptitude allowed for expanding the use of Green Completions into the Ghazeer development, which enabled zero-emission well testing of newly drilled wells even before commissioning of the new pipeline infrastructure. Through this initiative, the region has reduced emissions and generated cash by selling the recovered hydrocarbons instead of flaring into the atmosphere during well testing operations. Since Q1 2019, the total reduction of CO2 emissions exceeded 240,000 tonnes of CO2 equivalent, which equates to taking circa 52,000 vehicles off the road for one year. The implementation of this environmentally friendly operation also adhered to strict safety standards. The rigid bp safety process guidelines ensured that all challenges and optimization opportunities were fulfilled in a safe manner. The purpose of this paper is to detail how the team pushed the technical envelope to introduce this technology and share the journey entailing extensive cross-disciplinary cooperation amongst operations, subsurface and wells teams to fulfill the zero emissions objective.

Thermal EOR Conformance – A New Frontier for Asset Optimization: Steam Shutoff Pilot in Oman

Over the last 50 years, thermal EOR has been an effective method for reducing the viscosity of and recovering heavy oil from deep reservoirs. In mature thermal EOR projects, conformance is one of the main challenges for maximizing reserves and meeting long-term production expectations. In this paper, Occidental presents a novel pilot to address thermal conformance in the Mukhaizna field in Oman. This is a thermal EOR operation in deep reservoirs (> 2,000 ft) with extremely high viscosity (>10,000 cp) in harsh desert conditions with temperatures exceeding 500°F. The pilot area is a mature thermal area with 15 years of continuous steamflood operations. The novel conformance technique, based on a combination of chemical and zonal mechanical isolation systems, was developed in-house in a low oil price environment. The pilot area consists of multiple reservoir zones that have undergone vertical steam injection since 2005. Thermal conformance has emerged as a challenge because more than 60% of the injected steam has been preferentially entering the high-permeability zones, with only 40% of the steam entering the other zones, which hold a larger amount the remaining oil. The subsurface and well engineering teams collaborated to design a rigless operation using dual coiled tubing units, one for cooling water and one pumping a chemical gelation recipe that gels at a certain trigger gelation temperature at the target zone. Zonal isolation of the reservoir is achieved using a novel inflatable packer triggered mechanically by ball gravitation through coiled tubing at 500°F and retrieved after the temporary zonal isolation. The well and reservoir surveillance included gathering data for injectivity assessment, vertical injection logging, temperature profiles, tracer tests in offset producers, and well testing for determining water cut. The pilot improved vertical conformance, as injection logging showed 40% steam reduction was achieved in the target zone, and more steam was re-allocated to the shallow zones. In addition, there was a water cut reduction of more than 20% in offset producers, and oil production tripled over a period of 3 months, which paid back the cost of the pilot and generated positive cash flow. To our knowledge, based on an SPE literature search, this is the first successful thermal conformance operation conducted with the following combination of technologies: 1) Placing a novel chemical recipe through temporary zonal isolation with an inflatable packer, and 2) Using rigless operation of coiled tubing units at harsh conditions of >500°F and high pressure >1000 psi. The outcomes open a new frontier for thermal EOR development in multi-stack reservoirs, offering better utilization of steam injection and improving mobility control over the field life cycle. The cost of the pilot project was paid off in the first 6 weeks, and all chemicals used were developed in an eco-friendly system.