Control of Hydraulic Fracture Height Growth Above Water Zone by Inducing an Artificial Stress Barrier in Western Desert, Egypt
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Cited by 3 publications
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Evaluating the Feasibility of Waste Slurry Injection in an Oil Prospect in the Western Desert, Egypt
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.
Evaluating the Feasibility of Waste Slurry Injection in an Oil Prospect in the Western Desert, Egypt
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.
Frac Design Learnings from a Tight Sandstone Formation in Saudi Arabia
Cross-linked polymer has been utilized in the past to hydraulically treat the unconventional tight gas formations even though it has varying pay zone thickness that exhibits inconsistent lower stress barriers due to heterogeneities features of the field. Some of these reservoirs are connected with underlying water zones that have high potential to interaction with propped fractures due to absence of both clear stress barrier and inadequate net pressure which results in high water production. Petro-physical logs are analyzed and based on targeted net pay thickness the zone of interest are categorized as either having lower weak or strong stress barriers. Stress profiles derived from dipole sonic logs that runs across both the zone of interest and in shales (below and above the net pay) are calibrated with stress values from Mini Falloff Test (MFO) from offset wells. In addition, net pressure & leak-off properties are also calibrated. A Fully-3D modeling fracturing software was utilized to design the artificial barrier treatment using both slick water and hybrid fluid treatments and varying proppant volumes in order to simulate frac height growth with the aim of ensuring minimal or no contact with underlying water zones. Wells landed in different sand bodies sizes were considered and categorized under crest and core section of the field. Wells drilled in the crest section displays narrower, shorter pay zones and falls under the higher risk due to its proximity to the aquifers, while wells drilled in the core section of the field falls into the lower risk of communication with the water bodies due to its thickness. Generated height growth from frac simulations are analyzed for both slick water & hybrid frac treatment designs with varying amounts of proppant volumes. Simulated frac geometry were evaluated and the desired treatment types for both cases were selected based on the risk category. The preferential treatment type for the higher risk crest section of the field are slick-water and hybrid treatments respectively. Presence of adequate and inadequate stress barrier and the availability of decent net pressure based on MFO test were considered during the selection process. Estimated fracture height growth derived from post-frac evaluation pressure matches and production history matches were evaluated and results show adequate containment above undesired wet zone. In addition, offset well production comparison were performed which shows lower WGR during the initial productions for both wells as compared to existing offset wells that were treated with cross-linked fluid system. This paper introduces the stimulation design utilized to mitigate and minimize interaction with aquifers of zone of interest. The paper provides validation process to demonstrate how effective the artificial mitigation process can be irrespective of the proximity of the treated zones are to the underlying water zone. The validation process was performed after the mitigation treatment is pumped to evaluate the treatment. Recommendations for the design of future fracture treatments with close proximity to underlying water can be made based on sand bodies risk categories in which the well is landed. With adequate petro-physical log, mechanical information, and offset well data, treatment fluid type selection can be made based on desired fracture height growth. The knowledge gained with this study can be utilized to dealing with designs that involves proppant stimulation near water beds with inadequate stress barriers.
Integration Between Different Hydraulic Fracturing Techniques and Machine Learning in Optimizing and Evaluating Hydraulic Fracturing Treatment
Fracture geometry and conductivity are critical parameters for fracture treatment optimization, especially in cases that close to unwanted zones either water-bearing or gas zones. This study investigates the Artificial Neural Network (ANN) model for hydraulic fracturing optimization. The workflow begins with an integrated ANN model, then sets of variable fracture parameters and formation rock properties were utilized for training and testing the ANN based on the most appropriate activation function, the number of hidden layers and the number of neurons. The ANN model considers a 59 real field data of hydraulic fracturing treatments across the western desert of Egypt. The proposed ANN trained based on pressure transient test analysis that was conducted on the real field data. The available data was divided as 70% for training, 15% for validation, and 15% for testing. The optimum number of hidden layers and neurons was achieved after several trials. The proposed ANN model result was promising as compared with the common fracture simulation software. The cross plot of the actual fracture geometry parameters versus the predicted ANN outputs showed a good match with the correlation coefficient (R) for the whole data is 0.93. Then the relative importance of the ANN input parameter on the fracture geometry optimization was employed by the Garson method. The result of this work shows the potential of the approach developed based on the ANN model for predicting the fracture geometry.
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