Housingless ESPs for Slim Completion Wells

This paper describes a new electrical submersible pump (ESP) design concept to overcome the challenges of applications in slim well completions or thru-tubing deployment. The housing of the conventional pump is removed, allowing the pump impellers to have a larger diameter. The impact of this design change on pump hydraulic performance is assessed in this paper. Downhole ESPs operate in environments where space is limited radially. This is especially the case for slim completions or for thru-tubing rigless deployment. To provide the required rate and total dynamic head, the current approach is to use permanent magnetic motors and operate the slim systems at rotational speed over the conventional speed of 3500-4000 RPM. High-speed operations require new pump stage designs to minimize erosion and vibration. This paper provides an alternative pump design, which removes the pump housing with the benefit of increasing the impeller tip diameter, and hence potentially reducing pump length and operational speed. To ensure the pump retains the well fluids, the diffusers are designed to be externally threaded with an O-ring feature. The centrifugal pump affinity laws are applied to evaluate the impact of removing the pump housing and increasing the impeller outside diameter. A typical ESP housing wall thickness is about 0.18-0.25 inch. With the housing removed, the incremental space available for the impeller tip to occupy is increased by 0.36-0.5 inch. Analysis shows that, for the same pump speed as a conventional pump with a housing, a housingless pump will increase the head generated by 23-32%, and the rate capacity about 36-51%, depending on the pump series. In general, the smaller the pump outer diameter, the greater the flow and head capacity increase. This is because the available space due to removing the housing becomes a considerable size of the impeller tip diameter for the smaller series pumps. The elimination of pump housing enables impellers with a larger diameter to be used to generate more head per stage. In comparison to a conventional pump of the same outside diameter, and providing the same amount of total dynamic head, the housingless pump can have fewer stages and a shorter length or operate at a reduced speed. The reduced length can help mitigating pump-bending stress for installation in deviated or horizontal wells. The reduction in required operating speeds will reduce pump wears, heat generation and vibration. The housingless ESPs have applications for slim well completions or thru-tubing deployments.

Multi Zone Smart Well Completions Challenges in Highly Deviated Wells and Its Impact on Well Planning and Field Development

In multilayered reservoirs, major focus has been on the usage of smart well completion technologies to help improve recoveries, particularly with technological improvements and an increasing expanse of opportunities in more challenging and rewarding assets. The fundamental focus has been to design well completions that integrate several surface/subsurface sub zones and automate the flow control from each zone. In Multi zone Smart Completion Wells where significant investment is made to complete smart wells with remotely controlled inflow control valves (ICV), reservoir sweep & drain accessibilities becomes decisive when evaluating the efficiency of recovery and long-term field development strategy. Smart completion designs for multi-lateral wells present many challenges in terms of completion deployment and interventions in life of well. The complexity of operations increases with deviation, type of completion equipment, number of zones and planned interventions. In offshore, UAE a similar multilateral well was designed to be completed with 4 zone smart completion and had a mandatory requirement of accessibility to lower most drain (for future interventions) with the ability to plug the lower drain till future requirements arises. A solution is to utilize nipple & blanking plug in lower most drain, which was implemented in this well. Upon successful deployment of completion, plug was retrieved on coil tubing and lower drain accessibility was confirmed. However, during re-installation of blanking plug on coil tubing in deviated section, issues were encountered to pass through the ICV profiles. In attempts to pass through ICV profiles, blanking plug and running tool got disconnected from coil tubing, leaving the fish inside one of ICV valve. Several attempts were made to retrieve the blanking plug with rig on coil tubing without success by using thru-tubing fishing equipment options available in country. Well was suspend to work-out fishing strategy & evaluate availability of fishing equipment worldwide. Consideration was done for design and manufacture application specific fishing tools to perform workover with barge for such smart completion, as it includes a number of downhole components that makes its retrieval more challenging, and there are no standard procedure or provision in place to retrieve such complex completions in highly deviated section. A barge was mobilized with coil tubing, which performed the fishing operation as planned. Careful selection of equipment's, BHA and operational parameters resulted in successful retrieval of blanking plug & running tools. Accessibility to well was gain and confirmed. This paper presents the situation that was faced, the remedial work done to complete well, fishing operations and the subsequent factors considered for choice of equipment and operation on well. This paper concludes a detailed account of factors to consider for planning smart completions in horizontal multilateral wells & the successful fishing operation – an excellent example of how careful planning, dedicated project management, specialized design fishing tools, experienced personnel and a collaborative relationship between team's leads to a successful operation and prevented an extremely expensive workover of a high technology completion well.

A Geoengineering Approach to Maximum Reservoir Contact Wells Design: Case Study in a Carbonate Reservoir Under Water and Miscible Gas Injection

Maximum Reservoir Contact wells (MRCs) are a potential alternative to reduce the number of wells required to develop hydrocarbon reservoirs, improve sweeping efficiency and delay gas and water breakthrough. The well completions design is critical for the success of MRCs. In this study we present a case study of a MRC well completion design using Limited Entry Liners (LEL) in a mature carbonate reservoir under water and miscible gas injection. We developed an integrated workflow that considered a high-resolution numerical simulation model calibrated to static and dynamic data and wellbore-reservoir models coupling, for capturing the details of the flow interaction between both systems. Flow restrictions in the form of additional pressure drops to the flow from the reservoir into the wellbore were used to simulate the effect of small open flow areas, i.e.shot densities, in the LELs. Our work allowed identifying the most likely entry points of gas and water and design the well to minimize their impact on oil production. We observe that longer lengths open to flow outweighs the detrimental effect of producing from intervals closer to the water saturated zones. We also observed that balancing the inflow profile along the wellbore did not report beneficial results to oil production as it stimulates production from the reservoir zone from which the gas breakthrough is expected (middle of the producing section); this result is particularly relevant as it shows that designing the well completions with base only on static data could lead to poor production performance. The suggested completion for the MRC well encompasses four segments; a segment covering almost 50 % of the well length and located at the middle of the producing section with a blind liner (close to flow for gas control) and the remaining three with slotted liners with enough open area as to avoid causing significant pressure drops.

Joint Optimization of Well Completions and Controls for CO2 Enhanced Oil Recovery and Storage

Summary Carbon dioxide (CO2) enhanced oil recovery (EOR) is considered one of the technologies to help promote larger scale deployment of geologic CO2 storage because of associated economic benefits through CO2 storage, associated benefits of oil recovery, and the 45Q tax credit (a tax incentive that would reduce CO2 emission in the United States) as well as potential for utilization of existing infrastructure. The objective of this study is to demonstrate how optimal operation strategies (including well completions and controls) can be used to optimize both CO2 storage and oil recovery. The optimization problem was focused on joint estimation of well completions (i.e., fraction of injection/production well perforations in each reservoir layer) and CO2 injection/oil production controls [i.e., rates or bottomhole pressures (BHPs)] that maximize the net present value (NPV) in a combined CO2-EOR and CO2 storage operation. We used the newly developed stochastic simplex approximate gradient (StoSAG), one of the most efficient optimization algorithms in the reservoir optimization community, to solve the optimization problem. The performance of the joint optimization approach was compared with the performance of the well-control-only optimization approach. The superiority of joint optimization was demonstrated with two examples. In addition, the performance of co-optimization of CO2 storage and oil recovery approach was compared with the performances of maximization of only CO2 storage and maximization of only oil recovery approaches.

Innovative Method to Optimize Down Hole Control Valves by Well Modeling

The revolution of smart well completions has been significantly enhancing the oil & gas industry in the recent years, The completions allow for higher PIs, better sweep, longer well life, longer reservoir contact and better water management. These effects came into play and needed once O&G industry moved to drilling multi-lateral wells. This paper represents a tri-lateral well that was drilled with high reservoir contact. The production optimization was completed to evaluate the contribution of each lateral and decide on the future production strategy for the well. This evaluation also allowed to test the functionality of the Down Hole Flow Control Valves (DHFCVs). Further, determining this functionality allowed identifying cross flow between the ICVs and the laterals. The optimization included multi-stage testing of each lateral to ascertain the high oil & water contributors. The water contribution was recorded across each lateral to optimize the water production and enhance the well productivity. The productivity index was calculated using IPR modeling utilizing Pipe-Sim software based on the commingled multi-rate tests. To further plan the way forward on the well production, a flowchart was established during the optimization operation to guide through the optimization process, identify each lateral water contribution, and production strategy after the operation. This optimization has resulted in a significant cost avoidance, avoiding coil tubing horizontal logging intervention operations in all the three laterals. The details of the testing stages scenarios and the recommendations of the production strategies will be shared in this paper.

The True Market Value of a Good Petroleum Engineer: A Technical Perspective

Defined by SPE as the application of basic and engineering sciences to the finding, development, and recovery of oil, gas and other resources from wells, petroleum engineering (PE) has been throughout the years falsely thought of as an amalgamation of other disciplines applied to the exploration and recovery of hydrocarbons. Integrating all PE subdisciplines in a manner efficient for teaching and learning is essential for securing the abundance of well-rounded market-attractive professionals. This paper discusses advantages individuals with PE background experience should exhibit in their employment in the oil and gas industry and academia. There is no point for students in going to school for a degree that will not hand them a competitive edge within their discipline. For graduate PEs, the job market is dependent on the quality of their respective academic programs and by extension to the quality of the teaching faculty. A steady oil and gas job market may not necessarily warrant robust employment opportunities, particularly straight after graduation. In a discipline like PE, where almost everything that matters takes place thousands of feet underground, apportioning credit for successes or responsibility for failures is itself a challenge. Decreases in student enrollments in PE programs reported by various universities during times of low oil and gas prices poses questions about the future of the PEs discipline, despite the steady demand for oil and gas in the world's energy mix. Academic programs interested in facilitating a smooth transition of their graduates into the industry should work in conjunction with practitioners to provide the correct balance between theory and practice in their coursework ensuring that once employment opportunities are created, they get filled with candidates of relevant education and training. PE degree-holding candidates should be the natural first choice for PE positions. This means that their educational and professional backgrounds should be providing them with an undisputed advantage which places them a leg above candidates from other disciplines. For instance, for a well completions job opening, there should not be a better alternative than a good PE specialized in well completions. If every PE graduate comes out of his or her program with a skillset which is superior to that of his or her competition, he or she will be the preferred choice for an oil and gas job.

Using Machine Learning Methods to Identify Reservoir Compartmentalization in Mature Oilfields from Legacy Production Data

Despite long production histories, operators of mature oilfields sometimes struggle to account for reservoir compartmentalization. Geological-led workflows do not adequately honor legacy production data since inherent bias is introduced into the process of allocating production by interpreted flow units. This paper details the application of machine learning methods to identify possible reservoir compartments based on legacy production data recorded from individual well completions. We propose an experimental data-driven workflow to rapidly generate multiple scenarios of connected volumes in the subsurface. The workflow is premised upon the logic that well completions draining the same connected reservoir space can exhibit similar production characteristics (rate declines, GOR trends and pressures). We show how the specific challenges of digitized legacy data are solved using outlier detection for error checking and Kalman smoothing imputation for missing data in the structural time series model. Finally, we compare the subsurface grouping of completions obtained by applying unsupervised pattern recognition with Hierarchal clustering. Application of this workflow results in multiple possible scenarios for defining reservoir compartments based on production data trends only. The method is powerful in that, it provides interpretations that are independent of subsurface scenarios generated by more traditional workflows. We demonstrate the potential to integrate interpretations generated from more conventional workflows to increase the robustness of the overall subsurface model. We have leveraged the power of machine learning methods to classify more than forty (40) well completions into discrete reservoir compartments using production characteristics only. This effort would be extremely difficult, or otherwise unreliable given the inherent limitations of human spatial, temporal, and cognitive abilities.

Joint Optimization of Well Completions and Controls for CO2 Use and Storage

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 200316, “Joint Optimization of Well Completions and Controls for CO2 Enhanced Oil Recovery and Storage,” by Bailian Chen, SPE, and Rajesh Pawar, Los Alamos National Laboratory, prepared for the 2020 SPE Improved Oil Recovery Conference, originally scheduled to be held in Tulsa 18–22 April. The paper has not been peer reviewed. Carbon dioxide (CO2) storage through CO2 enhanced oil recovery (EOR) has been considered an option for larger-scale deployment of CO2 storage because of the economic benefits of oil recovery, 45Q tax credits, and the use of existing infrastructure. The complete paper investigates how optimal reservoir management and operation strategies can be used to optimize both CO2 storage and oil recovery. Results of the authors’ study showed that joint optimization of well completions and well controls can achieve a higher final net present value (NPV) than that obtained from the optimization of well controls only. Introduction In CO2 EOR associated with storage processes, poorly designed well-operating conditions or completions can lead to low oil recovery factors and suboptimal CO2 storage. Co-optimization of oil production and CO2 storage has been recognized as a feasible technique to maximize benefit in terms of oil production and CO2 storage tax credit. To the best of the authors’ knowledge, settings for well completions have not been considered as optimization variables in a CO2 EOR and storage co-optimization process. The objective of this study is to conduct joint optimization of well completions and controls [well rates or bottomhole pressures (BHP)] that maximize life-cycle NPV in CO2 EOR and storage processes and demonstrate the superiority of joint optimization over well-control-only optimization. Optimization Problem In this study, the optimization problem considered is the joint optimization of well completions and well controls for a CO2 EOR and storage process. The mathematical process behind this determination is detailed in the complete paper. The optimization problem was focused on jointly estimating the well completions (i.e., fraction of injection/production well perforations in each reservoir layer) and CO2 injection and oil-production controls that maximize NPV in a CO2 EOR and storage operation. The authors used a newly developed stochastic simplex approximate gradient algorithm to solve the optimization problem. The performance of the joint optimization approach was compared with the performance of the well-control-only optimization approach. In addition, the performance of the co-optimization of CO2 storage and oil-recovery approach was compared with that of the maximization of only-CO2-storage and only-oil-recovery approaches.

A Data Analytics Framework for Analyzing the Effect of Frac Hits on Parent Well Production

Well interference, which is commonly referred to as frac hits, has become a significant factor affecting production in fractured horizontal shale wells with the increase in infill drilling in recent years. Today, there is still no clear understanding on how frac hits affect production. This paper aims to develop a process to automatically identify the different types of frac hits and to determine the effect of stage-to-well distance and frac hit intensity on long-term parent well production. First, child well completions data and parent well pressure data are processed by a frac hit detection algorithm to automatically identify different frac hit intensities and duration within each stage. This algorithm classifies frac hits based on the magnitude of the differential pressure spikes. The frac stage to parent well distance is also calculated. Then, we compare the daily production trend before and after the frac hits to determine the severity of its influence on production. Finally, any evident correlations between the stage-to-well distance, frac hit intensity and production change are identified and investigated. This work utilizes 3 datasets covering 22 horizontal wells in the Bakken Formation and 37 horizontal wells in the Eagle Ford Shale Formation. These sets included well trajectories, child well completions data, parent well pressure data and parent well production data. The frac hit detection algorithm developed can accurately detect frac hits in the available dataset with minimal false alerts. The data analysis results show that frac hit severity (production response) and intensity (pressure response) are not only affected by the distance between parent and child wells, but also affected by the directionality of the wells. Parent wells tend to experience more frac hits from the child frac stages with smaller direction angles and shorter stage-to-parent distances. Formation stress change with time is another factor that affects frac hit intensity. Depleted wells are more susceptible to frac hits even if they are further from the child wells. Also, we observe frac hits in parent wells due to a stimulation of a child well in a different shale formation. This paper presents a novel automated frac hit detection algorithm to quickly identify different types of frac hits. This paper also presents a novel way of carrying out production analysis to determine whether frac hits in a well have positive or negative influence long-term production. Additionally, the paper introduces the concept of the stage-to-well distance as a more accurate metric for analyzing the influence of frac hits on production.

Novel Deployment of Tracers Leads to High-Confidence Results

A unique well-tracing design for three horizontally drilled wells is presented utilizing proppant tracers and water- and hydrocarbon-soluble tracers to evaluate multiple completion strategies. Results are combined to present an interpretation of them in the reservoir as a whole, where applicable, as well as on an individual well basis. The new approach consists of tracing the horizontal well(s) leaving unchanged segments along the wellbore to obtain relevant control group results not available otherwise. The application of the tracers throughout each wellbore was designed to mitigate or counterbalance variables out of the controllable completion engineering parameters such as heterogeneity along the wellbores, existing reservoir depletion, intra- and inter-well hydraulically driven interactions (frac hits) as well as to minimize any unloading and production biases. Completion strategies are provided, and all the evaluation methodologies are described in detail to permit readers to replicate the approach. One field case study with five horizontal wells is presented. Three infill wells were drilled between two primary wells of varying ages. All wells are shale oil wells with approximately 7,700 ft lateral sections. The recovery of each tracer is compared between the surfactant treated and untreated segments on each well and totalized to see how the petroleum reservoir system is performing. A complete project economic analysis was performed to determine the viability of a chemical additive (a production enhancement surfactant). Meticulous analysis and interpretation of the proppant image logs were performed to discern the cluster stimulation efficiency during the hydraulic fracturing treatments. Furthermore, comparisons of the cluster stimulation efficiency between the two mesh sizes of proppant pumped are also provided for each of the three new unconventional well completions. The most significant new findings are the surfactant effects on the wells’ production performance, and the impact the engineered perforations with tapered shots along the stages had on the stimulation efficiency. Both the right chemistry for the formation and higher cluster stimulation efficiencies are important because they can lead to increased well oil production. The novelty of this tracing design methodology rests in the ability to generate results with a statistically relevant sample size, therefore, increasing the confidence in the conclusions and course of action in future well completions.