Jarrett, Amber (Geoscience Australia, Energy Systems Branch) | Bailey, Adam (Geoscience Australia, Energy Systems Branch) | Hall, Lisa (Geoscience Australia, Energy Systems Branch) | Champion, David (Geoscience Australia, Mineral Systems Branch) | Wang, Liuqi (Geoscience Australia, Energy Systems Branch) | Long, Ian (Geoscience Australia, GA Laboratories) | Webster, Tara (Geoscience Australia, GA Laboratories) | Webber, Simon (Geoscience Australia, GA Laboratories) | Byass, Jessica (Geoscience Australia, GA Laboratories) | Gilmore, Stewart (Geoscience Australia, GA Laboratories) | Hong, Ziqing (Geoscience Australia, GA Laboratories) | Chen, Junhong (Geoscience Australia, GA Laboratories) | Henson, Paul (Geoscience Australia, GA Laboratories)
Shale gas plays require technology such as fracture stimulation to increase rock permeability and achieve commercial rates of flow. The brittleness of shales are a major control on the ease of fracture stimulation. The Brittleness Index (BI) is a proxy for rock strength, based on geomechanical parameters, and/or rock mineralogy, and provides an indication of hydraulic stimulation effectiveness. Legacy drill core does not always have the geophysical logs needed for assessment of shale brittleness, therefore mineralogical and geochemical derived proxies for shale brittlenesss are often used with varying success. Shales from the Paleoproterozoic Lawn Hill Platform of north-west Queensland and the Northern Territory are known to contain organic-rich sedimentary units with the potential to host shale-gas plays. The Egilabria 2 DW1 well demonstrated a technical success in flowing gas from the Lawn Supersequence and recent geomechanical logging in the Egilabria prospect have demonstrated the presence of brittle rocks favourable for fracture stimulation with similarities between logged geophysics and X-Ray Diffraction (XRD) derived brittleness (
You, Zhenjiang (School of Chemical Engineering, The University of Queensland) | Wang, Duo (School of Mechanical and Mining Engineering, The University of Queensland) | Di Vaira, Nathan (School of Mechanical and Mining Engineering, The University of Queensland) | Johnson, Raymond (School of Chemical Engineering, The University of Queensland The University of Queensland Centre for Natural Gas) | Bedrikovetsky, Pavel (Australian School of Petroleum, The University of Adelaide) | Leonardi, Christopher (School of Mechanical and Mining Engineering, The University of Queensland The University of Queensland Centre for Natural Gas)
New models for particle embedment during micro-particle injection into naturally fractured reservoirs are developed. The proposed models aim to predict production benefit from the application of micro-particle injection during coal seam gas (CSG) stimulation with broader applications to other naturally fractured reservoirs. The elastoplastic finite element modelling is applied to coal sample from Surat basin (Australia), to predict micro-particle embedment and fracture deformation under various packing densities and closure stresses. The coupled lattice Boltzmann-discrete element model (LBM-DEM) is then used for permeability prediction. These results are combined in a radial Darcy flow analytical solution to predict the productivity index of CSG wells. Modelling results indicate that considering elastoplastic fracture surface deformation leads to smaller permeability increase and less production enhancement, if compared with the linear elastic deformation of fracture implemented in traditional models. Although focused on Australian coals, the developed workflow is more broadly applicable in other unconventional resources. Modelling of particle transport and leak-off in coal fracture intersected with a cleat using LBM-DEM approach demonstrates the effects of particle and cleat sizes, particle concentration and sedimentation on the leak-off process. The leak-off is significantly affected if the particle-cleat size ratio is higher than 0.5. Particle sedimentation increases leak-off into vertical cleat substantially, but has no effect on horizontal cleat. Suspensions of higher concentration result in higher leak-off for cleats with different apertures.
To stimulate a reservoir efficiently, multistage plug-and-perf completion and fracturing technologies are widely utilized to create multiple hydraulic fractures along a horizontal wellbore. However, excessive field cases and lab tests evidenced that, the simultaneous initiation and propagation of multiple fractures within a stage could compete with each other, cause uneven fluid and proppant partition into each placed cluster. Resulting in low cluster efficiency and non-uniform fracture development. Solid particulate diverters can aid to influence the fluid distribution between open clusters to optimize stimulation efficiency. The objective of this study is to use numerical models to thoroughly investigate the functionality of particulate system in fracturing process and optimize the completion and stimulation strategy under specific downhole conditions.
In this study, both CFD-DEM model and a 3D fracture simulator are employed to model fluid diversion and fracturing process for wells completed with plug-and-perf technique. For a field case study, sensitive analyses were performed to quantify the impact of completion design and pumping strategy on the resulted stimulation efficiency. The overall conductive reservoir volume is predicted to compare the cluster efficiency between different design scenarios. Thereafter, the stimulation efficiency of placed perforation clusters is analyzed and optimized with engineered solid particulate diverters.
For the presented particulate diversion technique, both in-stage and inter-stage fluid diversion are operationally feasible. From our analysis, engineered solid particulate diverters can effectively plug the active perforation clusters and build-up enough pressure to divert fracturing fluid into non-active perforation clusters to create additional fractures. Proper number of diverter pills and adequate pumping schedule can boost the cluster efficiency and eventually increase the conductive reservoir volume.
Through a field case study, the presented geomechanical analyses showed that the diverter design and operational parameters can be customized to enhance cluster efficiency. By adjusting completion design, the usage of particulate diverters can be optimized accordingly to maximize the stimulation efficiency. With the proposed efficient design, all the planned perforation clusters can develop and propagate hydraulic fractures and contribute to the overall production.
Al-Nakhli, Ayman (Saudi Aramco) | Tariq, Zeeshan (King Fahd University of Petroleum and Minerals) | Mahmoud, Mohamed (King Fahd University of Petroleum and Minerals) | Abdulraheem, Abdulazeez (King Fahd University of Petroleum and Minerals) | Al-Shehri, Dhafer (King Fahd University of Petroleum and Minerals) | Murtaza, Mobeen (King Fahd University of Petroleum and Minerals)
Recent rise in global warming and fluctuations in world economy needs the best engineering designs to extract hydrocarbons from unconventional resources. Unconventional resources mostly found in over-pressured and deep formations, where the host rock has very high strength and integrity. Fracturing techniques becomes very challenging when implemented in these types of rocks, and in many cases approached to the maximum operational limits without generating any fracture. This leaves a small operational window to initiate and place the hydraulic fractures. Current stimulation methods to fracture these formations involve with adverse environmental effects and high costs due to the entailment of water mixed with huge volumes of chemicals such as biocides, scale inhibitors, polymers, friction reducers, rheology modifiers, corrosion inhibitors, and many more.
In this study, a novel environmentally friendly approach to reduce the breakdown pressure of the unconventional rock is presented. The new approach makes it possible to fracture the high strength rocks more economically and in more environmentally friendly way. The new method incorporates the injection of chemical free fracturing fluid in a series of cycles with a progressive increase of pressure in every cycle. This will allow stress relaxation at the fracture tip and correspondingly enough time for fracturing fluid to infiltrate deep inside the rock sample and weaken the rock matrix. As a result of which the tensile strength-ultimately the breakdown pressure of the rock gets reduced. The present study is carried out on different cement blocks.
The post treatment experimental analysis confirmed the success of cyclic fracturing treatment. The results of this study showed that the newly formulated method of cyclic injection can reduce the breakdown pressure by up to 24% of the original value. This reduction in breakdown pressure helped to overcome the operational limits in the field and makes the fracturing operation greener.
Pathak, Shashank (Cairn Oil & Gas, Vedanta Ltd.) | Ranjan, Ashish (Cairn Oil & Gas, Vedanta Ltd.) | Bohra, Avinash (Cairn Oil & Gas, Vedanta Ltd.) | Vermani, Sanjeev (Cairn Oil & Gas, Vedanta Ltd.) | Tiwari, Shobhit (Cairn Oil & Gas, Vedanta Ltd.) | Shrivastava, Pranay (Cairn Oil & Gas, Vedanta Ltd.) | Nagar, Ankesh (Cairn Oil & Gas, Vedanta Ltd.) | Ahsan, Mohammad Ayaz (Cairn Oil & Gas, Vedanta Ltd.) | Modi, Jaya Kumari (Cairn Oil & Gas, Vedanta Ltd.) | Upadhyay, Akhilesh (Cairn Oil & Gas, Vedanta Ltd.)
Mangala, Bhagyam & Aishwaraya Oil fields with ~669 wells produce about 20% of India's domestic crude production. As a part of production enhancement & sustenance activity various stimulation treatments were implemented from the initial development phase of these fields. Over time as these fields went from water flood to polymer flood, several modifications were made in stimulation treatment design to maintain the effectiveness of the stimulation treatments. Over last 8 years over 1100 stimulation treatment were executed in these field with most of the information kept within the treatment specific reports. To tap the value from this huge volume of information, a data structure was prepared to extract important learnings from these treatments. This paper details the workflow which was adopted to compile the historical unstructured data in a structure and details the crucial findings & learnings from the advanced data analytics applied on this data.
The primary objective of this work was to put unstructured data from 1100 stimulation treatment into a structured format. Information specific to the treatment design such as treatment fluid, volumes, concentrations, additives, pumping technique, soaking time etc. were compiled. This was also followed with wells specific information such as completion details, formation type, pre and post stimulation production/injection rates etc. Since the information volume was large and the data was scattered, a stimulation job code was defined which carried all the relevant information about any stimulation treatment in a simpler, scalable and structured format. The work was followed with advanced data analytics to extract value from this historical data spread over last 8 years. Stimulation performance indexes were defined to evaluate effectiveness of all these treatments which helped to identify root causes which led to some of the most successful stimulation treatments and helped to delineate learnings from unfavorable results.
The work identified the primary factors impacting the performance of stimulation treatments from broad field level to well & formation specific learnings. The overall findings included job specific learnings, findings specific to treatments fluid such as composition of chelating agent and its impact, concentration of HCl on injection improvement etc. as well as operational aspects while executing these jobs.
There are numerous technical papers on effectiveness on stimulation treatments and their design, this paper compiles the learnings from over 1100 stimulation treatments which provides a bridge between the theory and the practice while it also provides crucial insights on the operational aspects of these treatment as well which can impact the performance of these treatments. The paper also details the novel workflow adopted to structure the unstructured historical data to create substantial value.
To increase the likelihood of success of acid stimulation in limestone reservoirs, the treatment has to evenly cover the desired zone to allow controlled reaction rates that can result in a uniform conductivity pattern, or wormholes development radially across the pay zone. To achieve this ultimate goal, effective fluid diversion is required to reorient fluid path, from high to low injectivity areas. The selection of the right diversion technique is the key to obtaining successful stimulation results. Therefore, The objective of this work is to evaluate, and compare the stimulation efficiency of several diversion scenarios based on a highly reliable physics-based tool capable of simulating multiple completion types.
This work will be focused on two typical diversion methods applicable to perforated completions, such as: 1) ball sealers, and 2) bio-degradable particles. A coupled model that consists of wellbore and reservoir flow is used to simulate acid, and limestone rock interactions for each diversion method. The model simulates fluid hydraulics in the wellbore, couples it with transient reservoir flow, and accounts for the formation skin effects derived from each diversion technique. The model also considers the effect of induced wormholes generation and the created injection profile along the completed reservoir zone.
A horizontal well completion is presented to demonstrate the impact of each diversion approach in order to assess the effectiveness of a stimulation design. The most effective sensitivity combination of each diversion method is the focus of this work, and the treatment invasion distribution across the completed interval is compared to determine the best diversion approach. Different ball sealers geometries are considered to model irregular-shape perforation plugging efficiency and subsequent fluid diversion. The enhanced ball sealers model considers several physics parameters such as: inertial force, drag force, and ball-holding force along the wellbore during stimulation. On the other hand, the particulate diversion model includes an engineering model that is integrated into the wellbore-reservoir model to simulate the particle diversion.
The particulate diversion model is a binary system that consists of: (1) large particles agglomerate along the tapered path of wormhole, and perforations, and (2) small particles jamming effect to create a temporary sealed structure that reduces the permeability of flow path and builds a temporary filter cake on perforations that is capable of holding up necessary differential pressures to divert fluid to other low-injectivity zones.
The results show that the diversion efficiency depends basically on the length, perforationsconfiguration, and the reservoir heterogeneity. This case study demonstrates that particulate diversion offers the best alternative in terms of economic feasibility, and ease of application.
The current tool has the unique capability combined with an integrated approach to optimize diversion scenarios for matrix acidizing stimulation on limestone reservoirs to generate a more uniform wormhole pattern, avoiding fluid loss, and tapping into under-stimulated rock areas for production enhancement.
Ghadimipour, Amir (Baker Hughes, a GE Company) | Barton, Colleen (Baker Hughes, a GE Company) | Guises, Romain (Baker Hughes, a GE Company) | Perumalla, Satya (Baker Hughes, a GE Company) | Izadi, Ghazal (Baker Hughes, a GE Company) | Franquet, Javier (Baker Hughes, a GE Company) | Mahrooqi, Shabib (Petroleum Development Oman) | Dobroskok, Anastasia (Petroleum Development Oman) | Shaibani, Mahmood (Petroleum Development Oman)
As part of a multi-disciplinary investigation to optimize a tight reservoir development in the Sultanate of Oman, a comprehensive geomechanical characterization was performed and its results used as input for 3D non-planar hydraulic fracturing simulations. The simulation results led to better understanding of the reservoir response during hydraulic fracturing stimulation and thereby improved the decision making process for future field development. The focus of this paper is to highlight the geomechanical aspects of the analysis which explained several of the difficulties encountered during stimulation.
Geomechanical models were constructed covering the target sandstone and overlying clay-rich formation for ten horizontal and vertical wells by integrating diverse data including openhole logs, core rock mechanical tests, stress-induced failure interpretations from image logs, and stress measurements from mini-frac data. The geomechanical models were further supported by the results of available temperature, tracer and production logs. 3D geomechanical models were created by capturing the lateral and vertical variations of rock and geomechanical properties from these 1D models away from the wellbores, guided by the variations in seismic attributes using a co-simulation method. 3D modeling revealed a number of stress barriers supported by location of microseismic events in the target reservoir.
The geomechanical setting of the target formation is found to be complex with significant variations laterally and vertically. The West area of the field was found to have relatively lower stress compared to the Main area. Also, the Middle and Lower intervals of the target formation were shown to have considerably higher horizontal stresses (strike-slip/reverse faulting regime) compared to the Upper interval (normal/strike-slip faulting regime). The high stresses in Middle and Lower sections have the negative consequence of reducing the fraccability of these intervals as they require high breakdown pressures. In some cases, where breakdown was achieved, the resulting horizontal hydraulic fracture yields disappointing production results due to its inability to connect the reservoir vertically. Another important lesson learnt from geomechanical characterization in this field was the role of high angle bedding in truncating the vertical growth of hydraulic fractures. This understanding can further help to optimize the location of perforation intervals in stimulation designs of future development wells in this field.
Geomechanical characterization of this reservoir demonstrated considerable lateral and vertical heterogeneity that could only be captured by very detailed integration of well-based and seismic scale data. In addition, the effects of the
Sau, Rajes (ADNOC Offshore) | Kiyoumi, Ahmed (ADNOC Offshore) | Amin, Alaa (ADNOC Offshore) | Correia, Gladwin (ADNOC Offshore) | Barghouthi, Abdel Karim (ADNOC Offshore) | Almheiri, Alqasem (ADNOC Offshore) | Wheatley, Edward Jason (ADNOC Offshore) | Ali, Yasser (ADNOC Offshore) | Seabrook, Brian (ExxonMobil Upstream Integrated Solutions) | Angeles, Renzo (ExxonMobil Upstream Integrated Solutions) | Shuchart, Chris (ExxonMobil Upstream Integrated Solutions)
A giant carbonate field offshore Abu Dhabi is being redeveloped using extended-reach-horizontal-laterals up to 20,000 ft with open hole un-cemented liner, drilled from artificial islands. Long horizontal wells provide significant profitability in unit development cost; however it is critical to ensure effective stimulation of the complete lateral to maximize reservoir recovery. Earlier, SPE171800 introduced an innovative liner design for long open hole horizontal completions, namely Limited-Entry Liner (LEL) that enables high rate aggressive stimulation by bullheading technique. This paper will present the field stimulation results of more than five LEL laterals ranging several-kilometers in open hole completions, demonstrating the impact of LEL stimulations in accelerating production and maximizing reservoir recovery.
Several LEL horizontal wells were completed in low-permeability rock to enable high rate bullhead matrix stimulation. ExxonMobil proprietary software is used to design fit-for-purpose LEL that enables acid injection conformance along the lateral and at the same time creates deep-wormholes by high-velocity acid-jets through 3-mm/4-mm holes in liner base-pipe distributed non-uniformly along the lateral, compartmentalized with oil/water-swellable-packers. The execution of the stimulation campaign was made possible through the use of modularized-equipment packages installed on an ADNOC-vessel, utilizing a unique mechanism that locks the package components to frames installed to the vessel-deck. The stimulation package consists of 6×2000HHP pumps delivering up to 60bpm at 10,000psi. The liquid-additive system, 140bbl vertical mixing tank and more than 190,000gallon raw-acid storage tanks are fully automated to enable acid mixing and pumping on the fly at the desired rates, concentrations and recipes.
In order to demonstrate the effectiveness of acid placement and effective stimulation across the entire lateral, real-time Fiber-Optic surveillance techniques (DTS-DAS) were utilized. The recorded thermal and acoustic profiles provided a qualitative and quantitative measurement of the effectiveness of the mechanical diversion delivered by the LEL design. These data will help in corroborating and fine-tuning the model used in lower completion design of maximum reservoir contact wells in future field development. Along with well performance and real-time surveillance, production/injection logging data demonstrates effective stimulation of the entire lateral.
This paper presents field performance results from successful bullhead stimulation of extended reach horizontal well completed with LEL in low-permeability-reservoir. This paper also presents our first application of fiber-optic-DTS-DAS real-time-surveillance during stimulation and post-stimulation water injection. Advanced surveillance data demonstrated the success and effectiveness of the LEL completion and stimulation in extended-reach long horizontal open hole laterals.
The paper / presentation objective is to describe the achievement of the first gas lift well completed for multistage, hydraulically propped stimulation in a Romanian offshore field. The scope of the paper is to present the challenges and learnings associated with this well concept / design, engineering, modelling, equipment selection, yard testing, final design / program and offshore installation, operation, and results.
Reservoir depletion modelling indicated artificial lift would be required as early as 6 months within initial well start up. In order to effectively optimise production from the well for a longer range of well life cycle, a multi-stage stimulation sandface completion was selected and plans were made to install gas lift equipment during initial completion installation, prior to rig release. To meet the concept requirements, risks were assessed and case histories were investigated / incorporated during the planning phase to ensure reliability of performing high-pressure stimulations through gas lift (dummy) valves.
The material selection and specifications of the lower and upper completion equipment were defined considering: Artificial lift design Reservoir characteristics, Casing size, High pressure stimulation, Life of well operations
Artificial lift design
Reservoir characteristics, Casing size, High pressure stimulation, Life of well operations
Equipment suitability and compatibility considerations resulted in a few equipment selection changes, requiring yard trials to define optimum pulling / running tool string components and configurations, which were then applied offshore.
The final upper completion design consisted of gas lift mandrels (Gas lift dummies were replaced with gas lift valves following the HP stimulation), safety valve, permanent downhole pressure gauge and chemical injection mandrel. The lower completion consisted of hydraulic open hole packers, open hole anchor and open-close stimulation sleeves (all HP rated).
Collaboration within the multi-discipline and with multiple service providers was vital in developing the final, tested design and implementation in the offshore well. The current design in the well is showing great benefits in terms of production (a higher rate than expected) and cost (initial completion includes gas lift equipment already available for future potential use). The concept proof is considered to be of great success for upcoming projects and is increasing the confidence of the operator to develop and approach the upcoming wells with multistage stimulation gas lift completions.
This is the first well constructed in Romania that was hydraulically stimulated using proppant through an upper completion already having gas lift capability. A review of literature indicates this is an industry first. The success and communication of this well could provide benefit to the industry and could increase confidence when combining life-of-well requirements early in the well construction process.
The major challenges of shale reservoir development in Weiyuan gasfield are: (1)strong geologic heterogeneity, such as geo-stress, horizontal lamination, limited complexity and propagation of hydraulic fracture; (2)casing deformation, which caused the reservoir fractured insufficiently for many engineering problems. To avoid the problem above and increase complexity and SRV of hydraulic fracture, a deeply fracturing technology (DFT) was proposed, which was validated available and had been applied in 20s wells.
Based on ununiform distribution of geo-stress, the mechanism of DFT is using temporary plugging materials to fracture the reservoir sufficiently, which can be classified in 3 major patterns, include Intrasegment/Multi-segments/Closely spaced fracturing. Firstly, according to reservoir and stimulation objectives, choosing the appropriated development pattern. Then, considering geological and engineering factors, the optimization of temporary plugging materials and pumping parameters are needed in making pumping schedule. Finally, conducting fracturing by the schedule, and combined with operation curve and micro-seismic data, choosing proper time to release temporary agents.
With the application in the field, some conclusions are as follows:(1) Intra-segment development pattern was preferred in single-segment sufficient simulation; multi-segment was favored in the development of multi-stages without bridge plug situation, especially in the stimulation of casing deformation intervals. Which also improved operational timeliness; Closely spaced perforation pattern was benefit for the segment with big geo-stress difference and the well with small well spacing.(2) DFT was validated available by fracturing curve and micro-seismic monitoring. Event response points coverage rate of segment was 100%, SRV per segment and micro-seismic events were increase by 11%-45% and 54%-429%, respectively.(3) A combination of temporary plugging ball and powder was recommended, and the optimal agents pumping rate was 3m3/min. With the treatment above, pumping pressure was increased after agents released, the peak increment is 10 MPa, plugging effect was clear.
DFT is suitable for high heterogenous horizontal interval development, and also can be combined with bridge plug to achieve segment sufficient fracturing. The most important is, it is available in casing deformation interval stimulation, which is so serious in Weiyuan gas-field.