LEAN concepts have been applied in a wide range of industrial areas to identify and eliminate the waste in every stage of different processes, currently improve efficiency and lower production costs has become popular among Oil and Gas senior-level management. Minimizing waste is the base on which LEAN concepts are built. A LEAN endeavor seeks to eliminate activities or processes that consume resources, add cost or require unproductive time without creating value. The concepts can be described as striving for excellence in operations in which each employee seeks to eliminate waste and participates in the smooth flow of value to the customer. As part of a complete new strategy to ensure permanent improvements within the whole operational environment Petroleum Development Oman (PDO) has applied LEAN on drilling and other corporate core areas. This paper presents a LEAN application to optimize the Snubbing Interventions in order to ensure a significant CAPEX and OPEX reduction in an extensive deliquification campaign for gas wells thru the implementation of high end Velocity String (VS) completions. The projects involve the application of LEAN methodology from the early planning stages using in many cases re-engineering to the functional specifications, material selection and operational procedures. This re-engineering includes a deep review of every intervention activity, the application of new technologies and the analysis of major issues during previous snubbing interventions, followed by the measurement of the real operational times and deep technical brainstorming on every stage of the intervention process. All those factors have contributed with a significant amount of improvements along the intervention campaign.

In current depressed oilfield industry environment, economical and operational effectiveness becomes even more important especially in complicated, challenging projects that demand large investments and simultaneous utilization of multiple technical services. In Petroleum Development Oman (PDO), there are a few gas fields having similar downhole conditions with multiple target pay zones, whereas fracturing operations are complicated by the requirement of CT cleanouts and/or milling in between the stages. Multizonal and multistage frac operations are commonplace in oil and gas reserves around the globe, however despite of increased number of wells stimulated using specialist multistage completion equipment, the most often utilized completion design for this operation is still plug and perf, especially in vertical wells. There are also techniques on the market involving coiled tubing for perforation and isolation between the stages, however they have their own constraints and limitations, especially in high-pressure and high-temperature environment. For PDO wells, multistage completion technologies were not feasible, therefore conventional plug & perf approach had been selected as the optimum option. The main drivers behind this selection are the challenges associated with precise deployment of the completion jewellery across small pay zones and limited coverage of the target zones when using frac sleeves. Another constraint in the past was the pressure rating of the multistage completion systems existed on the market. Plug and perf completions are designed to allow pinpoint placement of isolation and reservoir access with on the fly adjustability. This means that there is more freedom in selecting desired perforation interval, plug-setting depth and no additional restrictions on the pumping rates that are incurred by CT string inside the tubing as in some of the popular techniques. The zonal isolation is the portion of the design that allows the frac treatment to address the target intervals without affecting the others. In operations requiring 15k+ differential pressure ratings, isolation becomes extremely challenging and requires robust and reliable technology to ensure true integrity so stimulations can be placed as per design. This challenge may get even worse with increasing temperatures, whereas conventional composite compounds are not applicable due to "swelling", or getting softer. The primary job of the frac plug is to isolate but operational safety and millability also must be taken into consideration for the overall efficiency of a completion design. Additional challenges in the target fields are the depletion of the zones and their extreme breakdown pressures that are not only exposing frac plugs to extreme differential stresses but also causing difficulties during milling operations, whereas maintaining balanced circulation becomes a primary task in order to prevent coiled tubing differentially or mechanically sticking in the wellbore. That is adding another requirement for the frac plugs - be easily millable and produce as small cuttings as possible to improve debris removal. The high pressures, high temperatures, aggressive fluids and long exposure time seen by isolation plugs in these frac operations had been a challenge for current treatment and completion designs due to availability (and reliability) of equipment and tools represented on the market, therefore Petroleum Development Oman and the frac service provider collaborated to engineer a successful solution. It involved multiple steps, such as development of the specific design requirements, integrity-testing criteria and field trials before the plug could be adopted for wide application. The target design was a plug with a ~3.45" maximum OD, having true 15k+ differential rating at ~400F+. This composite/metallic hybrid plug was supposed to be able to withstand the harsh downhole environment seen in the various PDO fields in Oman land operations and resolve multiple complications associated with well interventions in these fields.

In the last decade, hydrocarbon production from low-permeability reservoirs has been on the rise. Multi-stage hydraulic fracturing is the most common technology used to make production from such reservoirs economically viable. Radioactive-tracers and production logging, which are usually used to assess fracture flow efficiency, do not always provide reliable information in terms of the fracture effectiveness and total frac flow height. An advanced technique described in this paper not only can identify active fractured intervals but also quantify the inflow profile. A novel technique was developed to locate fracture inflows and quantify inflow profiles in hydraulically fractured wells. It builds on the industry-proven combination of Spectral Noise Logging and High Precision Temperature Logging. This technology was initially implemented for qualitative and quantitative analysis of reservoir flows, including those through leak points, cement, reservoir rock matrix and reservoir fractures. Fracture flow intervals are located using a new-generation of Spectral Noise Logging tool with wider dynamic and frequency ranges. Quantitative inflow profiles are derived by temperature modelling. The technology described in this paper allowed assessment of hydraulic fracturing effectiveness in the producing wells of Petroleum Development Oman. Three case studies are presented to demonstrate the application of this technology in two producing gas-condensate wells and one oil well, one vertical gas producer and the other horizontal, drilled into clastic low-permeability heterogeneous layer-cake reservoirs and therefore requiring multistage hydrofracturing for commercial hydrocarbon production. Production profiles were determined for all wells, with inflow splits between producing zones quantitatively analysed using temperature modelling, matching the recorded and modelled temperatures, pressures and phase compositions, and taking into account surface data, such as production history and separator test data, and PVT fluid properties. Spectral Noise Logging was used to determine the frac flow intervals. In the vertical well, the survey was conducted at three different flow rates to improve inflow quantification by matching three data sets. The survey results were used to successfully evaluate the effectiveness of multi-stage hydraulic fracturing and fracture height. The acquired information was used to improve hydraulic fracturing planning and design for the field. One of the advantages of applying this technique for fracture flow evaluation is its ability to survey wells under existing operating conditions without shut-in and production deferment. As opposed to conventional production log with spinner, described technique can locate and quantify flow behind pipe.

In recent years, horizontal drilling has become increasingly important to the oil and gas industry to enable efficient access to complex structures and marginal fields and to increase the reservoir contact area. New technologies have emerged during this time to address post-drilling intervention challenges in such wells. However, complexity of operations in horizontal wells is much higher than that of the vertical wells; therefore effectiveness of the selected technique has a major impact on the operational success and economics. In depressed market environment, economical and operational effectiveness becomes even more important especially when it’s down to complicated, challenging projects that require not only large investments but also simultaneous and continuous utilization of multiple resources, technical disciplines and assets. This paper reviews and compares different ways of horizontal multizonal well preparation for hydraulic fracture stimulation using plug & perf technique in challenging downhole conditions - differential pressures over 15,000 psi, presence of depleted zones complicating cleanout and milling operations between the frac stages, depth control issues. In PDO, there are some gas fields sharing similar downhole conditions whereas fracturing operations are complicated by the requirement of CT cleanouts and/or milling in between the stages. A horizontal well development trial has been implemented to evaluate its economic efficiency and prospects. Depending on the success of this trial, this approach can be spread to other fields with similar characteristics. In these trial wells, multistage completion technologies were not available due to either differential pressure limitations, downhole conditions or completion restrictions, therefore conventional plug & perf approach had to be applied. Such approach, in turn, becomes very challenging in horizontal wells crossing several different formations having multiple severely depleted intervals along the wellbore. These challenges include not only cleanout efficiency and precise depth control during zonal isolation and perforation but also conveyance capabilities. Several different techniques have been tried in PDO so as to discover the most efficient and economical way to complete this task: CT with deployed wireline cable, CT with fiber optic cable, DH tractors and conventional CT with GR-CCl tools in memory mode. All of them have their pros and cons and while saving some money in one small thing, a technique may cause major losses in the other and an operator needs to select the optimum approach taking into consideration multiple aspects. All technologies covered in the paper are well known in the oil business; however some of them were tried in an uncommon environment. For example, although not commonly used in horizontal frac applications (except for perforating for the first stage), tractors were used for plug setting and perforating between the stages and that required well cleaned wellbore for each run which is not an easily achievable task in a horizontal wells with multiple depleted zones. With certain measures aimed to improve their performance, tractors proved their efficiency; these measures are also discussed in this paper. Advantages and disadvantages of CT conveyance in comparison to tractor have also been discussed. E-line tractor technology has been successfully deployed in the Sultanate of Oman for reservoir surveillance using production logging assemblies in mature fields. Tractors provide specific advantages, as compared to other forms of conveyance, such as coiled tubing, and can successfully negotiate complex well trajectories in both horizontal openhole and cased hole well completions, enabling acquisition of good quality flow profiles in producers and injectors.

An integrated fracturing services (IFS) project between Petroleum Development Oman (PDO) and Schlumberger started in November 2009 and spanned a 7-year period until November 2016. It steered the local fracturing industry from standalone operations to an integrated package, offering collaborative services between hydraulic fracturing, coiled tubing, and well testing services. The synergies between the various services allowed for a more streamlined decision-making process between the operator and the service company. Ultimately, this led to faster well delivery times, lower non-productive time, and maximum utilization of personnel. The integrated approach was primarily based on communal resource pooling which was available for any of the services on location at any given time. At its prime, the IFS project comprised of 4 fleets deploying almost 300 employees across the Sultanate of Oman's northern and southern fields. The coordination process was centralized and handled by a dedicated team in charge of logistics, transportation, personnel, and resources. This centralization process was essential for the IFS workflow, and it was primarily managed by the service company in collaboration with the operator's well engineering team. Tangible results were achieved, and the IFS model added a new dimension to the fracturing industry in the Sultanate. It allowed the operator to align its well development operations with its production goals and delivery times. It also provided the service company with an opportunity to bridge operational and communication gaps, which would have been harder to achieve if other vendors were involved. These high-level results were coupled with operational successes by the fracturing, coiled tubing, and well testing crews. The novelty of this project is in the dynamism of all available communication channels, as well as the elimination of operational lag due to the reduced number of vendors in any given location. The success of the IFS program makes it PDO's first-choice fracturing model, especially during the current downturn when lowering operational costs is of utmost importance.