Presented at SPE Middle East Oil and Gas Show and Conference, Manama, Bahrain, March 2019.

Abstract

Oilfields produce huge amount of waste on daily basis such as drilling mud, tank bottoms, completion fluids, well treatment chemicals, dirty water and produced saltwater. These waste types represent a real challenge to the surrounding environment especially when the oilfield is located within a sensitive environment as in the Western Desert where there are natural reserves and fresh water aquifers. Waste slurry injection has proven to be an economic, environmentally friendly technique to achieve zero waste discharge on the surface over the past years. This technique involves creating a hydraulic fracture in a deep, subsurface, non-hydrocarbon bearing formation which acts as a storage domain to the injected slurrified waste. The objective of this study is to evaluate the feasibility of waste slurry injection in an oil prospect located in the Western Desert. The evaluation includes assessing the subsurface geology, recognizing the possible candidate injection formation(s), and designing the optimum injection parameters. Both geological and petrophysical data have been used to create the geomechanical earth model for an oil prospect located at Farafra oasis in the Western Desert. This model defines the mechanical properties, pore pressure, and in-situ stresses of the different subsurface formations. Afterwards, a fully 3D fracture simulator has been used to simulate the fracture growth within the candidate injection zone at different injection scenarios. Additionally, the fracture simulator has assessed the containment of the created fracture within the candidate injection formation(s) due to the presence of stress barriers above and below the formation. Finally, the formation disposal capacity has been calculated for each of the injection scenarios using a stress increment model. The geomechanical earth model shows that there is a good candidate injection zone which is upper/lower bounded by stress barriers. More importantly, it is located deeper than the local fresh water aquifer and thus no contamination is expected to the fresh ground water. In addition, the possible candidate is not a hydrocarbon bearing formation. A 3D fracture simulator has been used to determine the optimum injection parameters such as: the injection flow rate, the volumetric solids concentration, the slurry rheology and the injection batch duration. These optimum parameters are defined to minimize the stress increment rate over the well life, which ensure the highest disposal capacity and to contain the fracture within the candidate injection formation. Guidelines to conduct waste slurry injection technique in a new oil prospect that is located within a sensitive environment as in the Western desert are presented in this study. Also, the study highlights that this technique is economic for disposal of the different oilfield waste types in an environmentally friendly fashion.

Mohamed, I.M., He, J., and Nasr-El-Din, H.A.
Presented at Journal of Energy Resources Technology 135(1); 011301, 2013.

Abstract

Reactions of CO2 with formation rock may lead to an enhancement in the permeability due to rock dissolution, or damage (reduction in the core permeability) because of the precipitation of reaction products. The reaction is affected by aquifer conditions (pressure, temperature, initial porosity, and permeability), and the injection scheme (injection flow rate, CO2:brine volumetric ratio, and the injection time). The effects of temperature, injection flow rate, and injection scheme on the permeability alteration due to CO2 injection into heterogeneous dolomite rock is addressed experimentally in this paper. Twenty coreflood tests were conducted using Silurian dolomite cores. Thirty pore volumes of CO2 and brine were injected in water alternating gas (WAG) scheme under supercritical conditions at temperatures ranging from 21 to 121 °C, and injection rates of 2.0–5.0 cm3/min. Concentrations of Ca++, Mg++, and Na+ were measured in the core effluent samples. Permeability alteration was evaluated by measuring the permeability of the cores before and after the experiment. Two sources of damage in permeability were noted in this study: (1) due to precipitation of calcium carbonate, and (2) due to migration of clay minerals present in the core. Temperature and injection scheme don’t have a clear impact on the core permeability. A good correlation between the initial and final core permeability was noted, and the ratio of final permeability to the initial permeability is lower for low permeability cores.

Abou-Sayed,A., Abou-Sayed,O., Kholy,S., Almetwally,A., Loloi,M. , Mohamed, I.
Presented at J. Energy Resour. Technol. Dec 2018, 140(12): 122905 (9 pages)

Abstract

Underground injection of slurry in cycles with shut-in periods allows fracture closure and pressure dissipation which in turn prevents pressure accumulation and injection pressure increase from batch to batch. However, in many cases, the accumulation of solids on the fracture faces slows down the leak off which can delay the fracture closure up to several days. The objective in this study is to develop a new predictive method to monitor the stress increment evolution when well shut-in time between injection batches is not sufficient to allow fracture closure. The new technique predicts the fracture closure pressure from the instantaneous shut-in pressure (ISIP) and the injection formation petrophysical/mechanical properties including porosity, permeability, overburden stress, formation pore pressure, Young’s modulus, and Poisson’s ratio. Actual injection pressure data from a biosolids injector have been used to validate the new predictive technique. During the early well life, the match between the predicted fracture closure pressure values and those obtained from the G-function analysis was excellent, with an absolute error of less than 1%. In later injection batches, the predicted stress increment profile shows a clear trend consistent with the mechanisms of slurry injection and stress shadow analysis. Furthermore, the work shows that the injection operational parameters such as injection flow rate, injected volume per batch, and the volumetric solids concentration have strong impact on the predicted maximum disposal capacity which is reached when the injection zone in situ stress equalizes the upper barrier stress.

Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, September 2018.

A strong economy, industrial base, and low cost of living have led to a significant rise in population in the Greater Houston Metropolitan area of Texas, and with it, an increase in production of sewage and biosolids wastes. In the Houston area, sewage is treated with a combination of anaerobic digestion and lime stabilization to create biosolids which are then pelletized into fertilizer, composted, landfilled, or land applied.

The Slurry Injection technique is an alternative treatment and disposal method, that can replace much of the capital costs associated with maintaining and expanding the wastewater treatment infrastructure in Houston at significantly lower capital cost. This technique utilizes the principles of Drill Cutting Injection which has been implemented in petroleum industry since mid 1980s for oil and gas waste management. A biosolids slurry injection facility of sufficient capacity to dispose of all the biosolids currently produced by the city of Houston could be installed for less than 1/10 of the nearly $526 million in capital currently budgeted by the city to expand the current system under the current rolling 5-year plan. A substantial reduction in greenhouse gases is achieved as well, by using the slurry injection technology as the Carbon Dioxide and Methane (which are prominenet greenhouse gases) produced by biosolids degradation is completely sequestered under deep geological formation and along with it the emissions produced during dewatering and transportation of biosolids is also eliminated.

The City of Los Angeles’ Terminal Island Waste Water Treatment Plant facility has deployed the slurry injection technology since 2010. It currently disposes of approximately 20% of biosolids of the city of Los Angeles.

This paper describes the economic and environmental aspects related to biosolids management and the formation evaluation carried out to inject the bioslurry in greater Houston. The study includes both the economics of the surface construction requirements as well as the science behind the subsurface strata evaluation for containment assurance. For the subsurface aspects, a geomechanical and stress analysis is performed on two different formations (the Frio and the Vicksburg). A significant confining layer is present above and below our targeted injection zones, which restrict and assure the injected waste remains contained. Also, hydraulic fracture simulation and analysis provides an assurance and the waste containment within the engineered subsurface strata/formation for permanent storage.

Presented at SPE Annual Technical Conference and Exhibition, Dallas, Texas, USA, September 2018.

Abstract

A strong economy, industrial base, and low cost of living have led to a significant rise in population in the Greater Houston Metropolitan area of Texas, and with it, an increase in production of sewage and biosolids wastes. In the Houston area, sewage is treated with a combination of anaerobic digestion and lime stabilization to create biosolids which are then pelletized into fertilizer, composted, landfilled, or land applied. The Slurry Injection technique is an alternative treatment and disposal method, that can replace much of the capital costs associated with maintaining and expanding the wastewater treatment infrastructure in Houston at significantly lower capital cost. This technique utilizes the principles of Drill Cutting Injection which has been implemented in petroleum industry since mid 1980s for oil and gas waste management. A biosolids slurry injection facility of sufficient capacity to dispose of all the biosolids currently produced by the city of Houston could be installed for less than 1/10 of the nearly $526 million in capital currently budgeted by the city to expand the current system under the current rolling 5-year plan. A substantial reduction in greenhouse gases is achieved as well, by using the slurry injection technology as the Carbon Dioxide and Methane (which are prominenet greenhouse gases) produced by biosolids degradation is completely sequestered under deep geological formation and along with it the emissions produced during dewatering and transportation of biosolids is also eliminated. The City of Los Angeles’ Terminal Island Waste Water Treatment Plant facility has deployed the slurry injection technology since 2010. It currently disposes of approximately 20% of biosolids of the city of Los Angeles. This paper describes the economic and environmental aspects related to biosolids management and the formation evaluation carried out to inject the bioslurry in greater Houston. The study includes both the economics of the surface construction requirements as well as the science behind the subsurface strata evaluation for containment assurance. For the subsurface aspects, a geomechanical and stress analysis is performed on two different formations (the Frio and the Vicksburg). A significant confining layer is present above and below our targeted injection zones, which restrict and assure the injected waste remains contained. Also, hydraulic fracture simulation and analysis provides an assurance and the waste containment within the engineered subsurface strata/formation for permanent storage.

Badr S. Bageri, Salaheldin Elkatatny, Mohamed Mahmoud and Abdulaziz Al-Majed
Presented at International Journal of Oil, Gas and Coal Technology, 2018 Vol.19 No.2, pp.135 – 148

Abstract

In this paper, we evaluated the effect of sand content on the properties of the drilling fluid and filter cake during drilling a long horizontal section in sandstone reservoirs. Sixteen drilling fluid samples were collected and the initial properties were measured such as density and rheological parameters. HPHT tests were performed at 500 psi (the back pressure was 200 psi) to build the filter cake. The obtained results showed that the presence of sand caused significant change in the properties of mud and filter cake. The thickness of the filter cake increased about 35% to 40% of its original thickness. The mud yield point and 10 min gel strength increased by 40% due to the increase in sand content in the mud. Based on the real field data, empirical correlations were developed to predict the sand content in the filter cake using the drilling fluid properties.

Presented at SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, October 2017.

Abstract

Remote live monitoring of field operations, such as injection, has been very restricted, although real-time data are often collected at field sites. The difficulties lie in the data access and limitations to obtain computing resources for data analysis, which restricts the engineers’ abilities to provide useful and timely remote assessment and assurance to the operations. Cloud computing combined with web-based apps, however, makes it much easier and cheaper to monitor field operations in real time from anywhere around world. The current work provides our first attempt to apply the cloud computing and web-powered apps to monitor slurry injection at one injection site in Texas, USA. The site provides injection data that is stored automatically in a cloud database. The data are accessed and analyzed remotely through a web-based app in real time. Monitored injection pressure and rate provide the basis for pressure fall off analysis. If the fall off analysis yields an unanticipated fracture geometry, advanced 3D fracture simulations would be conducted to gain a better understanding of the effects of a specific injection on fracture geometry. The results of remote real-time data analysis set up early warnings to alert both onsite and offsite staff ahead of operational upsets. Compared to traditional desktop applications and isolated local data servers, cloud computing and web-based apps provide a more convenient and cost-effective way to monitor field operations in real time. The technique and workflow presented here may also be applicable to monitor other field operations.

I.M.Mohamed, O.Abou-Sayed, A.S.Abou-Sayed, A.Algarhy, .M.Elkatatny
Presented at Engineering Fracture Mechanics Volume 200, September 2018, Pages 208-217

Abstract

In a slurry injection application, the goal is to inject high solid content fluids (up to 25%). To accomplish this without plugging the near-wellbore pore space, the fracture is created using a pad of clean fluid. Once the fracture is open, the slurry is introduced to the formation. In some cases, where the formation has a high permeability-thickness product (k × H), a high injection flow rate is needed to open up the fracture with clean fluids. Most disposal wells do not have large enough pumps to provide high enough flow rates in these circumstances.

A combination of a lack of geomechanical understanding combined with poor injection or facility design leads some operators to create high formation damage around the wellbores in slurry injection applications by injecting slurry at flow rates which are insufficient to open fractures. When solids-laden fluid slurries are injected under a matrix flow regime, suspended solids will plug the near-wellbore pore throats and will form a filter cake layer at the formation face, causing the injection pressure to gradually increase. At the point where the injection pressure exceeds the formation fracture pressure, the formation will finally fracture. However, the near-wellbore filter cake remains a factor in future injection and leakoff characteristics. Moreover, the damage causes injection pressure to build up rapidly, facilitating the creation of short fractures which tend to cause near-wellbore stresses to increase more rapidly for a given amount of solid deposition than is the case with longer fractures.

Case studies have been presented in this paper which evaluates such slurry injection wells. Based on the data analyzed in this study, inducing the fracture with solids-laden slurry rather than with clean fluid by causes the injection pressure to continuously increase, ultimately leading to significantly reduced formation capacity. Recommendations are presented as well for how to avoid this condition even if the pumps do not have the capacity to provide the required injection flow rate using clean fluid. One such solution is to add a viscosifier to the clean pad fluid to raise the fluid viscosity which enables the creation of a hydraulic fracture at lower flow rate.

Presented at 52nd U.S. Rock Mechanics/Geomechanics Symposium, Seattle, Washington, June 2018.

Abstract

Slurry waste management may involve injection of solid-laden fluids with concentration up to 25%. To accomplish this without plugging the near wellbore pore space, a fracture is created first using a pad of clean fluid. In some cases, where the formation has a high permeability-thickness product, kh, high injection flow rate is needed to open up the fracture with clean fluids. Most disposal wells do not have large enough pumps to provide the needed flow rates. A combination of a lack of geomechanical understanding combined with poor injection or facility design leads some operators to create high formation damage around their wellbores in slurry injection applications by injecting slurry at flow rates which are insufficient to open fractures. Moreover, the damage causes injection pressure to build up rapidly, facilitating the creation of short fractures which tend to cause near wellbore stresses to increase more rapidly for a given amount of solid deposition than is the case with longer fractures. This paper presents one case study which evaluates the injection well using operational data.

Presented at Offshore Technology Conference, Houston, Texas, USA, April 2018.

Abstract

The E&P industry is rich in all types of data. Without proper database and analytics, companies are not able to retrieve and analyze the data they need in an efficient way. The result of the data management problems is that decisions are often made using incomplete or incorrect information. Even when the desired data is accessible, requirements for gathering and formatting it may limit the amount of analysis performed before a timely decision must be made. Strong data management is required to transform wells-related data into an integrated system of information. The key to successful data management is in the use of sophisticated platform-independent codes that doesn’t need any special setup or systems which allows easy transfer of information and data over the internet. This paper describes the data management and accompanying analytics approach taken in support of operations in Egypt to provide a shared knowledge system. This innovative cloud application provides a common interface to multiple systems in the organization, allowing a richer and more complete source of data to be used for decision making. Moreover, it enables the integration of static data, such as well logs in a particular region, with a real-time system to facilitate integrative real-time analyses using artificial intelligence, cloud-hosted physics-based simulators, or both. To support deepwater needs such as those in Egypt, the system incorporates productivity optimization analysis, reservoir geomechanics (pore pressure prediction, log interpretation, reservoir collapse, fault activation, subsidence, compaction, etc.), and data mining of key development uncertainty and well performance drivers.

Presented at Offshore Technology Conference, Houston, Texas, USA, April 2018.

Abstract

Development of assets in new frontiers can be quite costly, especially in deep-water and ultra-deep waters. These developments have many uncertainties, and each has an associated risk to both operations and project economics. Leveraging the fact that a significant amount of information has been (and continues to be) gathered in public and/or private domains for many of these assets/wells, a multi-year effort to build a data-mining framework for establishing whether well completion and production performance could have been accurately predicted during various stages of deep-water development (“Pre-Discovery,” to “Exploration,” through to “Mature Fields”) was undertaken. The final results of this work were incorporated into a selection/prediction software tool and database for decision support. The work helps establish priority for data acquisition and data values throughout asset development. The project created one of the largest privately held databases of GoM well information: five different publicly available and privately owned GoM datasets were integrated to obtain field-scale geologic and reservoir properties, well trajectories, schematics, drilling, completion and production data for thousands of fields and wells in the GoM. Multiple derived attributes were then calculated using Petroleum Engineering relationships to enhance the reservoir characterization and well performance comparisons. Historical well production data, together with periodic well test results, were used to calculate well productivity indices, skin factors and contacted volumes; changes in these values were analyzed over the course of each well’s lifecycle to determine its relation to completion designs, production practices and performances, and/or workovers. Rigorous data mining techniques, including a variant of Principal Component Analysis (PCA) and K-Means Clustering, were used to determine the most prominent attributes governing the intrinsic performance properties of reservoirs (“uncontrollable parameters”). Once subjected to clustering techniques, the uncontrollable parameters indicate several main performance clusters, each of which could be uniquely identified by its paleontology, rock type, reservoir properties and sedimentation/folding regime. Further, each main cluster was observed to be sub-clustered into groups – the wells in each such group having similar completion and production practices (AKA “controllable practices”). Petroleum engineering know-how was used to define well performance attributes and categories to analyze (“objective functions”), which in turn showed a strong relationship between uncontrollable parameters and controllable practices for the performance of each group of wells. Well performance can indeed be predicted with a certainty that depends on the data available: often to within 65%, 80%, and 95%, respectively, depending on the data availability at that stage of a given well’s development, from “Pre-Discovery,” to “Exploration,” through to “Mature Fields”.

Presented at Offshore Technology Conference, Houston, Texas, USA, April 2018.

Abstract

Appraisal is a key step in consenting to develop an asset, or abandoning it, and is pursued after successful drilling of an exploration well in a potential field. During the appraisal process the drainage area and original hydrocarbons in place, as well as ultimate recovery (EUR) from the field are estimated which are often based on minimum set of information gathered during the exploration phase. This lack of data, along with uncertainties surrounding the appraisal data, introduces high degrees of variations in pre- and post- sanction EURs (EUR). These estimates, however, are revisited each time new data becomes available and as a result, the EUR from a field, along with several other factors, is subject to change over the field lifespan. Identifying the key drivers in accurate pre-sanction estimation of ultimate recovery and reducing post sanction EUR variance, helps in resource allocation and sustainable field development. A major hurdle faced in subsurface characterization of assets is the degree of dependency between attributes and, the often non-linear behavior of these attributes. One way of overcoming these limitations is regression analysis; however, even in a high accuracy fit, regression coefficients by themselves are not necessarily good measures for ranking attributes, and elimination of lower ranked attributes would result in a new ranking of the remaining attributes. In the present study, several data mining techniques are applied on a dataset of 152 deep and ultra-deep water (D&UDW) fields in the Gulf of Mexico (GoM) to determine which of the 77 well-, reservoir- and field-scale attributes best capture the EUR variance for different fluid types in D&UDW fields in the GoM. Unlike the conventional regression approaches, the present study offers a robust and stable ranking of attributes with high accuracy fit, where low to none contributing (poorly-predictive) attributes can be safely removed without changing the overall ranking of higher attributes. This ensures that a high ranked attribute is indeed a major contributor to accurate estimation of the ultimate recovery from a field, and therefore is worth the investment for capturing its value; on the other hand, a low ranked attribute, in all likelihood, is a redundant attribute and should not be collected; this would in turn free up resources that can be allocated to acquisition of high(er) ranking attributes. Results of this study identify attributes that are strong overall drivers in over/under – estimation of reserves in pre- and post- sanction stages. We have also ranked the key attributes to reliable EUR estimations, which should be acquired prior to commitment to sanction. In addition, a set of attributes that have been consistently ranked as poor predictors are identified, which can be safely eliminated from data acquisition without affecting appraisal accuracy. Since the database tested was substantial covering all D&UDW fields in GoM, the identified key drivers have broad coverage and application.