Managed Pressure Drilling is one of several techniques gaining traction on critical wells with very tight pore and fracture pressure windows. In order to stay within these narrow mud weight windows it is critical to understand the bottom hole pressures. Some efforts have been made to combine surface modeling with downhole measurements during the actual drilling phase utilizing data sent to surface by mud pulse telemetry. However, during liner running and cementing operations this data is generally not available. Due to the narrow annular clearances around the liner and the heavier slurries used during cementing the chances of exceeding the fracture gradient are greatly magnified. To compound this during most cementing operations in managed pressure situations the surface measurements, and therefore the associated models based off them may bear no relationship to what is happening downhole, particularly as the cement can be effectively in freefall inside the pipe. Measurements can be, and are, compared both before and after the actual job, but during the critical time of the actual cement job and displacement there is often no indication of what is actually happening downhole. As stated above the telemetry system most utilized during drilling is mud pulse telemetry. However, as these systems occupy the pipe bore, and require a full mud column inside the pipe with a flow rate above a minimum threshold, then they are not used during cementing and liner running operations. To overcome these limitations a distributed measurement and acoustic telemetry network was run incorporated in the drillstring. This network sends data including annular and bore pressures, both from directly above the liner-running tool, but also distributed back along the string to surface. Acoustic telemetry transmits through the steel wall of the drillstring and therefore is independent of flow or fluid and can send data whilst tripping as well. Additionally the tools are fully through bore allowing the passage of cement darts and slurries with no real restriction. As the network also supplies interval measurements, then the passage of the different stages of the cement job can be seen as they move both down the pipe and back along the annulus. This paper will show, through actual field results, what is really happening downhole in the critical time of running the liner to bottom and during the managed pressure cement job. Results will be compared with traditional surface measurements. We will describe how we used downhole and interval calculations of friction factors and equivalent circulating densities to model what is happening in and around the liner during the cement job. We will discuss the application of the data, and the resultant algorithms and calculations derived from this to affect subsequent jobs and to improve decision-making and therefore the safety and efficiency of these critical cement jobs. As can be imagined the techniques thus described are new to the industry for real-time applications and further work is anticipated in delivery and interpretation of the results to further enhance this type of solution. A view forward will also be given in the conclusions on where this technology has the potential to go.
Infrastructure costs in the deep-water environment are expensive. There is therefore, both from a cost perspective, but also increasingly from an environmental perspective, an increased drive toward deriving more production from existing infrastructure. One example of this is going after additional reservoirs from the same platforms that may have initially been bypassed. This includes reservoirs that may have been technically challenging, or at the time considered uncompletable. To constrain uncertaintites in pre well construction models requiresrequire good data, from the right place, at the right time. Up until recently during well completion operations this has not been available in real-time from downhole. If we look at the world of drilling, then this has been revolutionized in the last 30 years by access to real-time downhole data. Far more complex wells are drilled, in increasingly complicated downhole conditions and geosteered through the reservoir sections utilizing real-time downhole data. Almost all other well construction activities have, to a certain extent, been operated using only surface data and models about what is happening downhole. In this paper we will look at technology that has been recently introduced that allows access to real-time downhole data by transmitting acoustic signals through the wall of regular drillpipe. This means that downhole and along string measurements of pressures, temperatures, weights and torque are now available to aid in decision making and to drive the efficiency of operations. This data driven approach to well completions will show through real examples how an operator moved from wells that were once considered uncompleteable, through initially stand-alone screens and then onto gravel packing the same reservoirs. Thereby improving both the initial production rates and delaying the time to intervention. This paper will further show how a gradual implementation of technology across a sequence of wells allowed for wellsite and onshore personnel to become familiar with and understand the limitations, and or benefits, of combining various technologies to meet the demands of the field. Technology implementation has often failed due to ingrained processes and personnel unfamiliar with the technology continuing to operate in the same way as previous. The technology is very important but we should not neglect the difficulties of implementing technology and allowing people to accept it's use.
The last several years has seen an increasing trend toward more depleted reservoirs and more challenging wells with tighter mudweight windows. Managed Pressure Drilling has been employed in these challenging well conditions, however industry take up has been slow for a number of reasons including technical, economic and deployment related. Those wells that have utilized Managed Pressure Drilling have tended to focus on the drilling related aspects of well construction. However, other areas of well construction such as casing and liner running and cementing and completion installation are equally and in some cases even more technically challenging. One area that has potentially hindered the uptake of Managed Pressure Drilling is that in general, and in particular in the well construction operations outside of on bottom drilling there has been no access to real-time downhole data. In particular this is related to real-time pressure data. Whilst cementing, displacing or completing then multiple fluid types and densities may be circulating both inside and outside the drillpipe, leading to significant challenges in simulations and models derived from surface data. To overcome this a new acoustic telemetry and measurement network is being deployed in depleted reservoir and managed pressure drilling operations to provide real-time downhole and along string measurements of pressures, temperatures and weights. Real-time data case histories will be shown from the Gulf of Mexico and the North Sea illustrating how this is being used to drive real-time decisions during drilling, cementing and completion installation operations in tight margin windows, depleted reservoir conditions and under managed pressure drilling operations.
Managed Pressure Drilling is one of several techniques gaining traction on critical wells with very tight pore and fracture pressure windows. In order to stay within these narrow mud weight windows it is critical to understand the bottom hole pressures. Some efforts have been made to combine surface modeling with downhole measurements during the actual drilling phase utilizing data sent to surface by mud pulse telemetry. However, during liner running and cementing operations this data is generally not available. Due to the narrow annular clearances around the liner and the heavier slurries used during cementing the chances of exceeding the fracture gradient are greatly magnified. To compound this during most cementing operations in managed pressure situations the surface measurements, and therefore the associated models based off them may bear no relationship to what is happening downhole, particularly as in certain circumstances the cement can be effectively in freefall inside the pipe. Measurements can be, and are, compared both before and after the actual job, but during the critical time of the actual cement job and displacement there is often no indication of what is actually happening downhole. As stated above the telemetry system most utilized during drilling is mud pulse telemetry. However, as these systems occupy the pipe bore, and require a full mud column inside the pipe with a flow rate above a minimum threshold, then they are not used during cementing and liner running operations. To overcome these limitations a distributed measurement and acoustic telemetry network was run incorporated in the drillstring. This network sends data including annular and bore pressures, both from directly above the liner-running tool, but also distributed back along the string to surface. Acoustic telemetry transmits through the steel wall of the drillstring and therefore is independent of flow or fluid and can send data whilst tripping as well. Additionally the tools are fully through bore allowing the passage of cement darts and slurries with no real restriction. As the network also supplies interval measurements, then the passage of the different stages of the cement job can be seen as they move both down the pipe and back along the annulus. This paper will show, through actual field results, what is really happening downhole in the critical time of the managed pressure cement job. Results will be compared with traditional surface measurements. We will describe how we used downhole and interval calculations of friction factors and equivalent circulating densities to model what is happening in and around the liner during the cement job. We will discuss the application of the data, and the resultant algorithms and calculations derived from this to affect subsequent jobs and to improve decision-making and therefore the safety and efficiency of these critical cement jobs.
Managed Pressure Drilling (MPD), along with variations such as Controlled Mud Level (CML), underbalanced drilling, mud cap drilling and drilling with losses, which will all collectively be referred to as MPD for brevity, is widely used to access reservoirs that cannot be safely or efficiently drilled into by using conventional mud pressure and circulating pressure to manage overbalance, well bore stability and a range of other concerns that are well known. MPD surface systems, of which there are many types and more detailed informationon on their functionality can be found in other papers, in conjunction with mud pulse based MWD systems transmitting downhole pressure are used to calibrate the whole wellbore system in a process known as finger printing, which is primarily used to calculate the frictional pressure drops around the entire system. These includes the surface pressure pumping equipment, the drillstring, annulus and back pressure system and chokes. The results of the finger printing are used as inputs to the MPD control systems to manage back pressures during the drilling of the well and these can be updated by using the MWD annular pressure measurements. This can be time consuming, but when combined with high accuracy flow meters has resulted in being able to successfully drill many wells.
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