This paper summarizes the results and learnings from the Autonomous Inflow Control Device (AICD) deployment and installation in multiple heavy oil fields in south Oman, allowing for swift utilization in other fields with similar characteristics. Those AICDs were mainly deployed and tested in those oil fields comprehensively, in horizontal producers, and the results were supported by rigorous lab tests was conducted to understand their behavior. This paper is a continuation of the work in reference [1]. In recent decades, horizontal drilling for producing wells became a widely known and used technology, this is due to the fact they improve the overall recovery, efficiency of production, drainage of the reservoir, as well as delay unwanted fluids (e.g. gas & water). However, this solution was not perfect, as due to highly fractured and heterogeneous reservoirs, premature water and gas production can and will take place, causing remaining oil to be bypassed, and hence, reducing the reservoir's recovery and eventually the profitability [2]. In south Sultanate of Oman, many fields have been developed with the use of the horizontal well technology, but together with its advantages, the geological nature of the formations and the physical properties of the produced fluids, have introduced important challenges regarding production optimization. One of the assets in question comprises of naturally fractured carbonate reservoirs drained through long horizontal open-hole completions. It has been developed with water flood and GOGD system. The main production optimization challenge faced for that asset is the fracture-dominated inflow, which leads to either high water or gas production. On the other hand, another asset where the trial took place comprises of shallow sandstone reservoirs of heavy oil, with strong bottom aquifers and high level of reservoir heterogeneities; fractures, faults and high permeability streaks are characteristic of these reservoirs. A horizontal well usually has a much higher capacity–as compared to a vertical well–for producing fluids at the same drawdown, hence, when talking on critical rates that do not disturb the oil-water-contact, horizontal wells will definitely have a higher critical rate than those of vertical wells, but even so, the capacity of moving fluids are bigger, causing faster movement of bottom water towards the horizontal well regardless [3]. Another field of the trial fields had produced heavy oil, with viscosities in the range of 600 cP to 1000 cP. The permeability is variable and in the range of 100mD to 10D. This makes the mobility ratio very favorable to water production. Some wells have started production with less than 10 % WC, but a sudden increase of WC has been observed up to above 90 %. Most of the wells have been completed with inflatable packers (EZIPs), creating 2 to 3 segments at the horizontal reservoir section. The AICD technology is suitable for being applied in this case of very low oil mobility and segments at the sand-face. The last trial field comprises of multi-stacked reservoirs, isolated by shale barriers, with production potential of oil from two main layers. The oil is light, ~ 42 API and 0.9 cp viscosity. Around 13 wells are closed-in due to various reasons including high water cut and low productivity. This field is producing since 1998 from 9 stacked reservoir zones-commingled, which provides a challenge to production allocation. Performing Production Logging Tests–PLTs-have not helped to improve the allocation issues. Water shut off is challenging when it comes to the point of deciding the zone required to be closed. Mechanical water shut off is an option to choke back the non-allocated water zones and allow more oil production. Although this field does not include horizontal wells, the total perforated length of the proposed well and the hydraulic natural isolation between the producing zones makes the application of the technology attractive for this field. An interventionless/wireless technology, which promotes uniform production along the entire length of a horizontal well, delaying the production of unwanted fluids (water or gas) from high productivity zones along the well path and promoting increased oil production from other compartments of the formation, would definitively represent a key aspect of the production optimization for these Petroleum Development Oman fields.
The multidisciplinary authors have summarized the results from the Autonomous Inflow Control Device (AICD) deployment in multiple oil fields, and presented it in this paper as a practice worth replication in a similar heavy oil environment, due its many benefits in optimizing field development. AICDs have been tested mainly in labs and controlled environments with few comprehensive field trials. This paper will form the basis for that which will add to the state of knowledge in the industry. The AICD technology was piloted in few wells of these fields. It comprises of mechanical devices installed with the sand face completion, which react in real time to the properties of the flowing fluids, decreasing/delaying the water influx (or gas if it would be the case) from high productivity zones, promoting increased oil production from other compartments of the formation, therefore, equalizing the drawdown along the horizontal section of the well and performing a dynamic water shut-off operation. No cables are required, as the devices work on the basis of viscosity and density difference between the oil and the water. The AICD-completed wells showed initial water cut in the range 1% to 2%. Which has reduced significantly in comparison to nearby analogues. The initial net oil rate resulted to be more than 2 times of the expected one, with an acceleration of ~10,000 bbls of net oil during the first month. After the initial production period, the technology is still delaying the aggressive water cut development usually observed in these fields, having provided 2 times the expected net oil rate during the first 3 months, with an acceleration of approximately 20,000 bbls of net oil over this period. It has been concluded that the application of the technology is successful and will be deployed as a baseline in all future horizontal wells drilled.
This paper summarizes the integrated technical learnings from the successful application of a an Autonomous Inflow Control Device (AICD) in new long horizontal wells producing heavy oil in multiple fields and show the result of extending this technology to the old producers in the field. It details the facts and observations that multidisciplinary authors have captured. The AICD was completed in more than 40 new oil wells in multiple fields. It comprises of mechanical devices installed with the sand face completion, which react in real time to the properties of the flowing fluids, decreasing/delaying the water influx from high productivity zones, promoting increased oil production from other compartments of the formation, therefore, equalizing the drawdown along the horizontal section of the well and performing a dynamic water shut-off operation. The great successful result from new oil wells with this technology AICD opened the door to do few trials in existing producers. The AICD-completed wells showed initial water cut in the range 1% to 2%. Which had reduced significantly in comparison to nearby analogues. The initial net oil rate resulted to be more than 2 times of the expected one, with an acceleration of ~10,000 bbls of net oil during the first month. After the initial production period, the technology is still delaying the aggressive water cut development usually observed in these fields, having provided 2 times the expected net oil rate during the first 3 months, with an acceleration of approximately 20,000 bbls of net oil over this period. It has been concluded that the application of the technology is successful and already deployed as a baseline in all future horizontal wells drilled. Also this technology was tried in old producer wells and already 15 wells completed with AICD completion which shows good reduction in gross/water and increase in oil production in some of the wells by more than 30%. With these successful results, 35 wells from existing producers were planned to be completed by AICD in 2020 from multiple fields. The authors have summarized the results from the AICD deployment and presented it as a practice worth replication in a similar heavy oil environment, due its many benefits in optimizing field development. AICD in new and old wells will be a game changer in all filed to reduce the water and increase the oil.
Advancing technology in thermal recovery and declining conventional oil resources are leading to the increased application of thermal heavy oil recovery processes. Heavy oil resources in carbonate rock are estimated at 1.6 trillion bbl, one-third of which is in the Middle East, making it a crucial part of the global energy supply. A thorough understanding of reservoir properties (including but not limited to natural fracture systems, fluid saturation, permeability and rock matrix) is fundamental to optimizing recoveries with existing uncertainties, where efficient optimization through simulation can lead to the application of optimum operational decision parameters combined with improved understanding of the significance of such uncertainty parameters.Steam-assisted gravity drainage (SAGD) provides many advantages compared to conventional surface mining extraction techniques and alternate thermal recovery methods. These advantages include significantly greater per-well production rates, greater reservoir recoveries, reduced water treating costs, and dramatic reductions in steam-oil ratios (SORs). However, carbonate reservoirs exhibit varying properties in terms of porosity, permeability, and flow mechanisms. Many other engineering considerations exist for SAGD, including recovery rate, thermal efficiency, capability and economics of drilling horizontal well pairs, steam quality, steam injection rate, steam pressure, sand production, reservoir pressure maintenance, and water intrusion. In this study, such parameters are simulated and optimized by coupling a numerical reservoir simulator with commercial optimization software featuring exploratory, gradient, and direct methods. A dual permeability approach to modeling naturally fractured reservoirs is used.The results are discussed and the significance of both uncertainty and decision parameters is outlined in addition to the added benefits of optimized solutions using various optimization techniques. The results and observations show significant improvement using the optimum combination of decision parameters, such as steam injection rate, pressure, and temperature, to improve recoveries with a good understanding of the significance of uncertainty parameters, including rock and formation properties, in addition to overburden conditions that can affect the SAGD process. Reservoir management requires effective risk management where a sound understanding of uncertainties is fundamental to success. This study outlines all of these parameters in a comparative way, which can be useful in future industry applications.Modeling fractures in carbonates in heavy oil reservoirs is not an easy task because of the modeling and computational difficulties. It is important to have solid thorough examples, including building the model, setting up the optimization workflow of uncertainty, and outlining the results in a comparative manner to enhance understanding for more efficient reservoir management during SAGD processes.
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