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The acquisition of downhole pressure data representative of reservoir response enabling subsequent pressure transient analysis has been one of the primary drivers for running drill stem tests. However, many factors can influence the representativity and interpretability of the data acquired that are not related to reservoir properties.

To our knowledge, while many publications have presented challenges in acquiring representative pressure data those have not been compiled in a comprehensive revies, and there are no practical recommendations that would summarise causes and effects and offer procedures to eliminate or at least manage those effects and enable end-users to maximize the value of acquired data.

This paper describes in details today's challenges associated with the acquisition of high-quality, representative and undisturbed bottom hole pressure data during well test operations. Many different effects, including gauges’ deployment methods, wellbore effects and operational aspects of the test can compromise the quality of bottom hole data acquired while running a welltest.

Therefore, the origin and impact of each of these effects needs to be evaluated at the design stage of the test to develop appropriate mitigation actions. To address these issues, actual examples and methodologies derived from various locations are presented.

Over the years the metrological performances of downhole memory gauges such as resolution or drift have improved drastically, reaching a point where gauge specifications have become less influential on data quality than environmental effects. Many improvements have also been made in DST tools to increase the representativity and interpretability of acquired bottom hole pressure data such as the introduction of downhole shut-in valves or compensation for tubing contraction and expansion due to temperature change during the test. However, there remain several occurrences today where memory gauge data are affected by the various wellbore phenomena making interpretation of downhole pressure transient test data complicated. The selection of an appropriate location of pressure sensors in the DST string also remains a crucial task.

The paper provides analysis, explanations and practical recommendations allowing to mitigate the most common effects typically observed during welltest operations performed around the world, such as: –

Tidal effect

This paper will summarise the observation and lessons learned from hundreds of welltest operations performed around the globe with different reservoir fluids and environments through a few telling examples. Furthermore, the paper provides practically proven well-test techniques allowing to manage those adverse effects on bottom-hole pressure data. Recipes for success are provided to ensure that high-quality data can be acquired during welltest operations in a challenging environment while keeping the cost in line with the AFEs.

For two wells, performing continuous N₂ lifting in an offshore environment for weeks to produce a large quantity of aquifer water that had crossed into oil-bearing zones during a long shut-in period would involve high operational and logistical risks and require a large capital investment, which was not proven economical. As an alternative, a Rigless coiled tubing (CT) gas lift system, which uses gas cap energy, was chosen as an efficient, reliable, and cost-effective technique to revive oil production from the two offshore wells.

The technique involved running CT inside the production tubing. The CT was then hung up on an additional tubing hanger installed on the production tree. The injection rate and injection pressure were supplied by a choke manifold connected to a gas well that had high wellhead pressure. The gas was injected down continuously through CT, which lifted the standing water in the production tubing annulus to surface. Production logging tools, simulation models, and flow performance applications were used to

Estimate the volume of water crossed into oil-bearing zones

The CT gas lift system was found to be the most efficient and cost-effective way to revive production from dead wells. In this application, the free available energy of the only gas well in the field, which was drilled in the gas cap, was used to supply the required gas rate and injection pressure.

The following steps were completed with the collaboration of all parties:

Successful installation of CT in production tree via additional retrievable tubing hanger

As expected, each well took nearly 45 days of continuous lifting to reach the pre-estimated water cut for the wells to be self-lifting. CT was then successfully retrieved, and the wells continued flowing naturally with considerable rates. The oil rate gain for both wells was around 4,000 BOPD.

This methodology has been approved and adopted by the operator for future similar cases as a cost-effective method to revive oil production from dead wells.

The novelty of the technique comes from the utilization of gas cap energy in the form of high wellhead pressure of the only gas well in the field, which was drilled in the gas cap, as a source of injection pressure and injection rate. This innovative technique made reviving dead wells possible without changing wellhead configuration or investing in weeks of costly N₂ kickoff operations.

Smith Flow Control's TorkDrive prevents manual valves from being damaged by excessive torque application during valve operation. It can be customized to suit most manufacturers' handwheel operated valves when a torque monitoring of more than 59 ft-lbf is required. The device is a customizable add-on tool that minimizes the risk of plant or process shutdown and unnecessary repair costs through valve overtorque. It can be specified as a simple, standalone unit mounted on the valve input handwheel or directly to the valve input shaft; or it can be used in conjunction with the EasiDrive portable valve actuator, a nonimpacting, air-driven power tool designed to simplify valve operations.

Approximately 20% of all oilwells in the world use a beam pump to raise crude oil to the surface. The proper maintenance of these pumps is thus an important issue in oilfield operations. We wish to know, preferably before the failure, what is wrong with the pump. Maintenance issues on the downhole part of a beam pump can be reliably diagnosed from a plot of the displacement and load on the traveling valve; a diagram known as a dynamometer card. We demonstrate in this paper that this analysis can be fully automated using machine learning techniques that teach themselves to recognize various classes of damage in advance of the failure. We use a dataset of of 35292 sample cards drawn from 299 beam pumps in the Bahrain oilfield. We can detect 11 different damage classes from each other and from the normal class with an accuracy of 99.9%. This high accuracy makes it possible to automatically diagnose beam pumps in realtime and for the maintenance crew to focus on fixing pumps instead of monitoring them, which increases overall oil yield and decreases environmental impact.

90% of Field T production relies on Gas lift as means of artificial lift. Typical surveillance strategy in assessing the health of the gas lifted wells is to deploy flowing gradient survey (FGS) in tandem with surface welltest. However, in the case of Field T, this technology meets its limitation in investigating prolific wells due to its current well mechanical condition and dual string completion environment. Welltracer technology application in the field has broken the barrier in evaluation of these wells in Field T.

The Welltracer application is a non-invasive data acquisition method which measures the travel time and concentration of the CO2 return which is introduced upstream of the gas lift header. The interpreted results allow for the identification of injection points and rate. This simple idea opens up opportunity for gas lift performance evaluation of wells in Field T that was not possible through the conventional approach of FGS. This breakthrough is vital for Field T as some of the wells are facing either one or more of the following problems i.e. dual string wells with gas robbing issues, tubing leak, restricted tubing due to pack-off and multi-point injection.

Twenty-three surveys and analysis were completed during the first application in Field T. The opportunity identified from the survey were categorized depending on the resources and timeframe required to execute the changes. Four enhancement opportunities were identified which only required surface valve manipulation were executed immediately and showed instant results. Other than additional barrels, the results of the campaign have a tremendous value of information that changed the earlier comprehension of the existing problems in some of the wells.

This paper discusses the results of the application of the technology in Field T. This paper will also elaborate on the lessons learned and improvement recommendations in terms of project identification, execution and planning. Another important highlight that will be discussed is the limitation and assumptions made to further enhance the understanding of the Welltracer technology.

In the onshore field in the Northern part of Thailand, the wells are typically produced with gas lift and converted to beam pump later, using the annulus space for gas separation. In the past, the completion string must be replaced to switch to beam pumps. However, with the new Hybrid completion, the existing completion can be used, and the amount of workover is reduced. In the new Hybrid completion, two sliding sleeves are installed in the tubing string, allowing us to utilize both artificial lift methods without replacing the tubing. To produce the well with gas lift, both sleeves are closed, and the well is produced normally. When converting the well to be produced with a beam pump, both sliding sleeves are opened, a plug is set above the lower sleeve, and a downhole pump installed above the upper sleeve. This forces the wellbore fluid to flow out to the annulus through the lower sleeve. Since the liquid level is higher than the upper sleeve, most of the gas travels up the annulus while the liquid traverses through the upper sleeve from the annulus into the tubing. The liquid is then pumped along the string with a beam pump. This method acts as a gas separation mechanism to prevent gas lock and reduce efficiency problems for beam pumps. The flexibility to switch between the two artificial lift methods allows us to handle the dynamic wellbore and reservoir conditions more efficiently. The Hybrid completion has enabled us to (1) handle a wider well productivity range, (2) significantly lower the cost of workover, (3) decrease the hazards exposure during operations, and (4) produce oil and gas faster, favoring the economic return.

Successfully deploying a single trip completion system in a deep-water environment requires an innovative technical solution to address the risks that come with this environment. Following a request from the operator for a deep-water single trip solution, a number of different system options were proposed. Each system was evaluated against the operator’s requirements, and a Radio Frequency Identification (RFID) technology-based system was selected as it offered the greatest flexibility in both activation and contingency methods to meet the demands of the project.

It was proposed to hold a 2 stage System Integration Test (SIT) at a test rig in Aberdeen. The first SIT was performed with a small number of tools that could be setup in different modes to prove the system’s logic against the operator’s expectations. Whilst this was conducted successfully a number of learnings and operational optimisations were captured. These were fed into a full-scale SIT which was deployed at the same test rig. This second SIT involved a complete representation of the single trip system and was designed to test the final system logic prior to deployment into an offshore environment.

The system was then installed successfully in November 2018, on a subsea well, offshore Nigeria with no intervention. It resulted in an operational time saving of at least 60% over the previous best recorded time for a conventional two-trip completion from the same rig. This represented a step change in operational efficiency and will now be the operator’s base case completion methodology as they develop the field further.

This is the first time a single trip completion has been deployed in this fashion in a deep-water, offshore environment. The demonstrable step change in operational time and resultant project OPEX savings, proves that the use of RFID and remote actuated tools within completions offer excellent alternatives to traditional methods.

Most major projects fail(Merrow, 2011). Failure results from a lack of control Failures occur most often and most ruinously on our largest and most important projects. But these are the projects that are subjected to the most rigorous management oversight and control. There appears to be a paradox here: Those projects that we control the most rigorously appear to be the most out-of-control. We argue that this paradox is caused by control models rooted in the reductionist/Newtonian worldview that is not suitable for understanding and controlling today's complex projects. We argue that management control models can be improved by making them more like the control models extant in naturally occurring complex systems which do not experience any paradox of control.

While many factors in the reservoir cannot be controlled, there are three controllable factors in field development that make a significant impact. More reservoir contact leads to more oil produced. Controlling sand and water means lower treatment costs, and in-situ reservoir management leads to higher cumulative production. While the underlying technologies have been around for up to 20 years, it is only recently that their synergies and true value are understood. This paper will demonstrate the effect each of these technologies has on increasing overall production rates, improving recovery, and reducing the cost per Barrel of Oil Equivalent (BOE).

The successful implementation of multilaterals in the North Sea will be analyzed. Since 1996, over 300 multilateral junctions have been installed on the Norwegian continental shelf fields with currently approximately 30 junctions completed each year.

Additionally, simulations will be used to demonstrate the incremental improvements in oil recovery that can be obtained by using properly designed advanced completions that include multilaterals, sensors, and passive/active flow control equipment.

The paper will evaluate production performance of a vertical well field development base case against scenarios using horizontal and multilateral wells. It will show how fields can be optimized, leading to increased oil and decreased water production.

Production rates can be significantly improved by combining multilaterals with other advanced completion techniques, such as intelligent completions and inflow control devices. The subject field simulation can be further optimized to manage gas and water production.

With a tailored multilateral field design, combined with properly designed advanced completions systems, the simulation succeeds in terms of achieving maximum contact with the oil reservoir and meeting improved ultimate recovery objectives.

It can be concluded that as reservoir contact is increased, a reduced decline in production rate is observed leading to both a higher Estimated Ultimate Recovery (EUR) and optimized drawdown profile distributions. Additionally, results will be presented that have considered oil production and a method to lower production of unwanted fluids or gas.

This paper also demonstrates the value of field development design from the perspective of reservoir simulation. It is through reservoir insight that a level of understanding is created that can help define the optimum well and completion design to meet field expectations.

Advanced multilaterals continue to grow in popularity with many operators, and it therefore becomes important to evaluate the value of different field development methods. This knowledge can aid operators in unlocking new reservoir targets and optimizing field development, and ultimately will improve recovery factors and overall field economics.