Displacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water-wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing, and cement liners. In many situations, the negative differential pressure cannot be tolerated, and the risk of failure at the liner top, etc., is increasedespecially, if the wellbore has not been pressure-integrity tested. Additionally, with increasing rig/spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates.To overcome the density limitation of these cleaning fluids, conventional techniques, such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (e.g., water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is used. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency. Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology.This paper describes the field applications of new brine-based, high-density, solids-free cleaning fluids in balanced-displacements in deepwater and offshore shelf wells. The new high-density fluids were based on new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, a maximum pumping pressure of more than 9,000 psi was expected for conventional water-based displacement but was reduced to a little more than 3,000 psi with the new design. Highdensity cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and used successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

TX 75083-3836, U.S.A., fax 1.972.952.9435. AbstractDisplacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing and cement liners. In many situations, the negative differential pressure cannot be tolerated and the risk of failure at the liner top, etc. is increased, especially if the wellbore has not been pressure integrity tested. Additionally, with increasing rig / spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates.In order to overcome the density limitation of these cleaning fluids, conventional techniques such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is utilized. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency.Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology.This paper describes the field applications of new brinebased high-density solids-free cleaning fluids in balanceddisplacements in deepwater and offshore shelf wells. The new high-density fluids were based on, new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, maximum pumping pressure of more than 9,000 psi was expected for conventional water based displacement, but was reduced to a little over 3,000 psi with the new design. High-Density cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and utilized successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

Typically, deepwater subsea completions are characterized by significant production rates which require large completion hardware. Slim-hole designs (defined as 5½" production casing and smaller) are usually avoided due to increased risk and production concerns. However, as the deepwater Gulf of Mexico basins grow more mature, sidetracks and challenging new drills become frequent. Sidetracks out of 7¾" to 7" production casing are being performed, ending with 5½" or 5" casing at TD. Additionally, many new drills either have to penetrate multiple depleted intervals or require more aggressive directional plans to reach smaller targets. Both scenarios can result in slim-hole designs. Historically, the two (2) riskiest phases of the completion are wellbore displacement and sand control. This paper presents the design, the risk assessment, the installation and the actual results for three (3) subsea slim-hole deepwater completions. A summary of the completions are as follows:5" Frac Pack (FP) at 74 degrees deviation5" FP with > 40000 md-ft kH sand5½" High Rate Water Pack (HRWP) at 25000 ft TVD As a result of proper planning, the Case Histories were successfully executed in Gulf of Mexico deepwater. However, performance expectations from these type wells must be risked and managed. Completion Challenges Completion operations in deepwater are very challenging and are even more challenging in a slim-hole design. Slim-hole completion challenges include:Small completion tools which result in limited injection rate, sand volume, and treatment lengthsSmall workstrings create high treating pressures due to friction during wellbore displacement and sand control operations.Small tubulars limit production due to erosional velocities.Small completion tools limit the options available for "positive" mechanical fluid loss devices. With high spread rate costs, any non-productive time (NPT) is magnified. Planning is critical for success. Mitigating Risk Complete the Well on Paper (CWOP). One of the best ways to mitigate risk is to review the plan with as much knowledge and experience as possible. A CWOP provides a very effective way to achieve this goal. CWOP meetings are usually conducted for two (2) days with the rig crew and the responsible contractors. The completion procedure is reviewd in phases with small breakout groups. Operational recommendations are captured, and a technical limit curve is established. A CWOP was performed for all three of the Case Histories discussed in this paper. Case Histories The data presented are from three (3) deepwater Gulf of Mexico field Case Histories. A general well information summary table is included in each section. Wellbore Displacements As identified earlier, the first critical phase of slim-hole completion operations is wellbore displacement. Each Case History had similar issues including the following:High differential pressure (Mud in hole / seawater)Limited standpipe pressure (SPP) rating: 4500 psiTapered workstrings (High friction)Large completion fluid volumesLimited pit capacityTwo (2) exposed liner tops

TX 75083-3836, U.S.A., fax 1.972.952.9435. AbstractDisplacing drilling mud with clear solids-free completion brine is a critical step during well completion. As we move into deeper waters and drill to deeper depths (greater than 25,000 feet MD), conventional methods and cleaning fluids become a limiting factor in this phase of the operation. Conventional cleaning fluids use fresh water or seawater treated with surfactants to remove wellbore solids and water wet tubulars. Using low-density cleaning fluids creates a negative differential pressure between the working kill weight fluid and the formation, casing and cement liners. In many situations, the negative differential pressure cannot be tolerated and the risk of failure at the liner top, etc. is increased, especially if the wellbore has not been pressure integrity tested. Additionally, with increasing rig / spread costs, high pump rates are necessary to decrease the time it takes to perform these operations. The pump rate is indirectly proportional to the pump pressures required. Weighted spacers decrease the overall pressure differential, which allows for higher pumping rates.In order to overcome the density limitation of these cleaning fluids, conventional techniques such as additional hydraulic horsepower, backpressure schedules, the addition of solids to lighter cleaning fluids (water, seawater), or balancing the weight of the low-density cleaning fluid with a matching higher-density fluid is utilized. However, each of these "fixes" has inherent limitations and is accompanied with reduced cleanup efficiency.Furthermore, conventional surfactants are not active or effective in high-density brines. New brine-compatible surfactant chemistry and the corresponding balanced-displacement engineering design were developed to overcome limitation of conventional displacement technology.This paper describes the field applications of new brinebased high-density solids-free cleaning fluids in balanceddisplacements in deepwater and offshore shelf wells. The new high-density fluids were based on, new surfactant technology developed to ensure effective wellbore cleaning, wellbore design parameters, and displacement modeling. In addition, weighted spacers aid in reducing high pump pressures and wellbore pressure differentials. In one case history, maximum pumping pressure of more than 9,000 psi was expected for conventional water based displacement, but was reduced to a little over 3,000 psi with the new design. High-Density cleaning fluids, with densities up to and greater than 17.5 ppg, have been formulated and utilized successfully without compromising cleanup efficiency and significantly reducing differential pressures. Results from laboratory development and field applications are presented.

Oil and gas industry is increasingly approaching more challenging situations where it is of primarily importance to carefully assess the technical solutions to maximize productivity, to evaluate the economic worth of investment and identify all the risks and opportunities involved in the project.A challenging subsea well is planned to be drilled and completed in a deep offshore field in the Adriatic Sea (Italy). This project includes all the challenges and criticalities related to: deepwater wells, sour environment, gas lift wells, multilateral and intelligent wells.The objective of the study was to provide decision support for the selection of the most suitable multilateral and completion design addressing, through a probabilistic approach, all the uncertainties regarding reservoir characteristics, well design and productivity in terms of duration and cost.A multidisciplinary working team, including drilling and completion engineers, geologists and reservoir engineers, has been created in order to assess all the aspects of the project with its opportunities and criticalities.Different scenarios have been compared with regards to the available technologies for multilateral and intelligent completions.The first step of the analysis was the identification of the uncertainties (opportunities and risks) related to technical, organizational or environmental issues, successively reported in a probabilistic time and cost model.A dedicated fault tree approach was deemed useful to focus on the combination of events leading to a potential branch loss and to calculate the associated probability.All uncertainties were then combined with production profiles into a technical unit cost ($/bbl). This paper describes workflow and results. The results provide the managers with a comprehensive picture of a complex issue to make the investment right decision at a given confidence level.This should provide a guideline to engineers, geologists and managers on the risked approach for the development of complex projects.