Patent Application
20220307322
The present invention refers to a method of drilling a maritime wellbore with fluid reverse circulation without using tubulars connecting probes to the well, called a drilling riser, which can be applied in maritime wellbores that are built with the use of single or dual activity probes, such as deepwater or ultra-deepwater offshore wells, with the primary function of increasing operational efficiency and reducing the cost of drilling a wellbore.
In drilling of oil wellbore in deepwater there are several challenges, one of which is the need to use a large amount of drilling riser joints. Each joint has high weight (about 32,000 lb or 15 ton) and large dimensions (about 23 m long and diameter of 21 in). Another challenge is the demand for a greater capacity of the fluid circulation system's tanks. Just to fill the riser tubulars, a volume of the order of 470,000 liters (3000 bbl) is required for a water depth of 2,500 m. A third challenge is the need to use pumps with a higher flow rate to allow the transport of gravel inside the riser.
In addition to the technical challenges, there are also economic issues, since offshore probes have a high daily operating cost. The probes currently correspond to around 50% of the wellbore construction cost and are paid per day worked. In addition, other services performed are also paid per day available or per day worked. The lowering of the riser tubulars, in particular, is an activity that requires a lot of hours. In maritime wellbores with water depths greater than 1,500 m, several days are spent in the well construction stage, due to the long way to be traveled in the maneuvers due to the stretch of sea.
The traditional solution for drilling in deeper water depths has been the adoption of riser tubulars with thicker wall and probes with more pumps and greater load capacity. However, there is an alternative solution under study for almost two decades, which is to perform operations without riser tubulars. In the typical suggested configurations, subsea pumps are adopted for the return of the fluid with gravels (US20160047187A1), or concentric columns are used (US20170058632A1). However, the use of subsea pumps introduces a low reliability component into the system. In addition, it adds complexity to the set, as it changes the riser tubulars, which are components without movable parts and with a low failure rate, by subsea pumps, with movable parts and a high failure rate.
On the other hand, to increase operational efficiency and reduce costs, it is attempted to reduce the total time of well construction. One way to do this is to perform as many operations as possible—in parallel. For example, load transfer and movement operations are almost all carded out in parallel. Likewise, the equipments that will go down the wellbore are prepared hours or even days in advance.
Thus, some systems were proposed that allow that other operations leave the critical path and be performed in parallel. One such proposal is the use of dual activity probes (patent EP1277913B1). These probes allow the performance of some operations simultaneously, in each of the towers, removing the fastest operation from the critical path. However, its advantage is limited to situations where the BOP (Blowout Preventer) and the riser pipe are not positioned at the wellhead. When the BOP and the riser pipe are connected, all operations are necessarily performed through a single path.
The drilling technique with fluid reverse circulation was implemented from 2006, to improve cleaning efficiency of gravel in critical hydraulic scenarios in the onshore wells, being described in patent PI0605527-3B1.
Document PI0605527-3B1 method for drilling wellbores with fluid reverse circulation used to remove gravels resulting from this operation. The method consists of using an annular isolation rotating device that allows pumping the fluid to remove the gravels through the annular space formed between the drill string and the well wall. This fluid reaches the bottom hole, penetrates the drill string, through the drill holes, and carries the gravels to the surface of the drill string. The fluid is diverted, at the top of the drill string, to a gravel separation unit, where the gravels are separated from the fluid. The fluid is conveyed to the storage tank, where it is aspirated by a pumping unit and then pumped back into the annular space of the well. For the application of the method, it is necessary that the annular space is isolated from the atmosphere by an annular isolation rotating device. Unlike the present invention, the description refers to drilling with reverse circulation in onshore wells, where drilling risers is no longer used. In the present invention, the proposal is a reverse circulation drilling in offshore wells without this equipment.
The method of the present invention refers to a process of drilling a marine wellbore with fluid reverse circulation without using drilling riser tubulars. In this case, the return of the fluid with gravels occurs through the interior of the drill string and the injection of clean fluid is made through the annular of the well. In the operation, the use of the riser tubulars as a flow line for the fluid return with gravels is disposed, using instead the drill string itself. As a result, the operation of lowering the drilling riser tubulars, which lasts for days and has a high cost, becomes unnecessary.
For dual activity probes, the arrangement of this invention allows the use of the two towers even after connecting the BOP, something that is not possible with the use of the drilling riser tubular connected to the BOP. Thus, operations such as mounting and lowering the casing can be performed in parallel with the drilling operation of the previous phase, allowing a significant additional gain of time.
The document WO2013077905A2 provides an equipment packages and control methods using two or more lifting systems that operate simultaneously and continuously in a synchronized manner such that the feeding of tubular into or out of a well is achieved with continuous or near continuous movement, without the need for periodic interruptions. The drilling and tripping equipment packages and control schemes are also able to rotate the tubular in the wellbore with continuous speed and torque sufficient for both drilling and back-reaming operations. The drilling and tripping equipment package and control scheme is additionally able to circulate drilling fluid into the internal bore of the tubular with sufficient pressure and flow to facilitate both drilling and back-reaming operations, with minimal interruption to circulation.
Also, the document WO2013077905A2, despite dealing with a method to simplify oil well drilling processes, seeking to reduce the time lost mainly during the process of removing the drill string, does not reveal how the operations, such as mounting and casing lowering can be performed in parallel with the drilling of the previous phase, allowing a significant additional gain of time, such as the method of the present invention. In particular, the patent deals with a continuous circulation system. It has no connection with the proposal to withdraw the drilling riser, such as this invention.
Document KR101707496B1 refers to a method of assembling/disassembling various pipes for drilling simultaneously with a drilling operation, a blow-out preventer (BOP), and installing/disassembling a Christmas tree so as to shorten the drilling time, which is a conventional problem. The auxiliary structure for the drilling operation is installed on the deck of the drilling rig to perform the auxiliary operation for the drilling operation simultaneously or independently with the drilling operation by the derrick. Although the document offers a drilling method with the objective of reducing drilling time, it uses drilling risers, unlike this invention. The subject patent refers to the use of probes with an auxiliary table. The withdrawal of the riser and the use of reverse circulation does not directly require the probe with auxiliary table, nor the probe with two tables. Using a two-table probe when drilling without riser, as exemplified in U.S. Pat. No. 6,085,851A, leverages the advantages of operation, which does not occur with the auxiliary table probe.
Document EP1277913B1 refers to a multi-activity device on a drilling probe, having two towers and multiple tubular activity stations inside the tower, in which the primary drilling activity can be conducted from one of the towers and, simultaneously, another drilling activity (auxiliary) can be conducted from the other tower, to reduce the critical path length of the well construction activity. According to the document, it is possible to perform some operations simultaneously; however, its advantage is limited to situations where the BOP and the riser are not positioned at the wellhead. When the BOP and the riser are connected, all operations must be performed, mandatorily, by the tower where the BOP is positioned, which is different from the present invention in which the arrangement allows the use of more than one tower even after the BOP is connected.
As will be further detailed below, the present invention refers to a process of drilling a marine wellbore with fluid reverse circulation without using drilling riser tubulars, with different characteristics and that provide advantages in relation to what is revealed by the documents of the State of the Art.
The present invention refers to a method of drilling a marine wellbore with fluid reverse circulation without using drilling riser tubulars. In reverse circulation drilling, the return of the fluid with gravels occurs through the interior of the drill string and the injection of clean fluid is made through the annular of the wellbore. Thus, having a rotating head on or inside the BOP, the use of the drilling riser tubular as a flow line for the return of the fluid with gravels is disposed, using instead the drill string itself. For the kill and choke lines, as well as for fluid injection, rigid or flexible lines can be used.
This eliminates the need to use drilling riser tubulars, thus releasing the load capacity in the probe, in addition to the space occupied by this equipments. It also eliminates the need for large volumes of fluid to fill riser tubulars.
Unlike proposals present in the State of the Art, the entire operation can be done without the need for subsea pumps, equipments of high complexity and low reliability, and without the need for concentric columns, unconventional equipments, complex, of difficult handling on the probe and with inferior drilling performance.
Additionally, the method of this invention makes the operation of lowering the drilling riser tubulars unnecessary, which lasts for days and has a high cost. This allows for savings of millions of dollars in the construction of the wellbore.
Finally, for dual activity probes, the arrangement allows the use of the two towers even after connecting the BOP, something that is not currently possible with the connection of the drilling riser tubulars to the BOP. Therefore, operations such as mounting and lowering the casing can be performed in parallel with the drilling operation of the previous phase, allowing a significant time gain.
Some of the objects to be achieved by the subject of the present invention are:
The present invention will be described in more detail below, with reference to the attached figures which, in a schematic form and not limiting the inventive scope, represent examples thereof. In the drawings, there are:
Preliminarily, it is noted that the following description will start with the preferred embodiments of the invention. As will be apparent to any person skilled in the art, however, the invention is not limited to these particular embodiments, but rather to the scope defined in the claims.
Numerous variations focusing on the protection scope of this application are allowed. Thus, it reinforces the fact that the present invention is not limited to the particular configurations and embodiments described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1020210053836 | Mar 2021 | BR | national |
