Globally, many thousands of potentially productive oil and gas wells suffer internal corrosion due to H2S, CO2, and other produced gases and liquids. This limits their capability to provide a packer sealing area suitable for traditional mechanical production packers. Total E&P Qatar planned a recompletion using intelligent well technology in a well in which they expected to find some corrosion. Before initiating the recompletion, they investigated the use of alternative packer technology. Swelling elastomer packers have been used worldwide in many applications, but verification was required in this case to assess whether such packers would hold pressure in a corroded section of casing. In addition, testing was also was needed to assess whether the completion could be pulled in the event that it became necessary to retrieve the components from the well. A swellable packer with multiple cable feed-through was designed and manufactured to approximately two-thirds size of the originally specified packer. A sample of corroded casing, supplied by Total E&P Qatar, was used to build a test jig. The jig was equipped to simulate and record pressure, temperature, and other downhole conditions. Theoretical simulations were performed to assess the force required to overcome the anchoring forces applied by the swelled elastomer and were verified by a pull test. It is expected that with a reliable sealing mechanism for these older wells, technically and financially viable workovers and re-completions can be performed, thereby extending field life and adding to recoverable reserves. This paper describes the application and test procedures along with the verification and results of the testing performed. Introduction The Al Khalij field lays 100km offshore Qatar in 60m water depth. The first discovery dates back to 1991, when the Mishrif reservoir was confirmed as oil bearing. The field was developed in a phased manner to reduce developmental risks and to optimize development cost. First production from the field was delivered in 1997. At the end of 2005, three phases of development of the field had been completed, and currently, an infill drilling program is in progress. Presently, this vast field is produced through seven unmanned wellhead platforms and one water-separation platform. A total of 37 oil producers, six water injectors, and four water producers have been drilled and completed to date. Due to the proximity of the aquifer, significant amounts of water are produced. Owing to the sub hydrostatic reservoir pressure, producer wells are equipped with Electrical Submersible Pumps (ESPs). The electrical generation necessary to power the ESPs is located on Halul Island, located 45 km away from the field as shown in Fig. 1. Most of the water produced is separated offshore on a process platform and is re-injected into the field with the water injector wells aiming at sustaining reservoir pressure. Additional water is produced from the Umm Er Radhuma shallow aquifer and re-injected into the Mishrif reservoir in order to achieve a full voidage replacement and further sustain reservoir pressure.1,2 The Mishrif carbonate reservoir is comprised of several thin stacked layers (three to five meters thick) with a wide range of permeabilities (five to 300mD). In order to increase the Productivity Index and the drainage area of the oil producer wells, they usually feature long to very long cased horizontal drains, which are among the most ambitious ones in the industry. Nearly all wells drilled after year 2000 feature drain lengths in excess of 2000m (see Fig. 2).

R.K. Bratli*, G. Hareland**, F. Stene*, G.W. Dunsaed* and G. Gjelstad*** Abstract This paper presents the introduction, application and verification of a new drilling optimization approach. During the past decades rate of penetration (ROP) models for all types of drilling bits were developed and verified. The unique software uses these models in a new approach that optimizes the drilling cost on each hole section. The simulation of ROP every foot gives the capability to simulate the effects of all operating conditions, bit design, bit wear and formation properties. All the penetration rate models used can be inverted to solve for rock strength if ROP, operating conditions, lithology percentage and field reported bit wear is known. This imply that if one well has been drilled, and the penetration rates are inverted, a foot by foot strength is obtained, by integrating over each individual bit run until the field reported bit wear matches the calculated. This strength is then used as input for simulation, and it is shown that the drilling cost for one particular 12,25" section can be reduced as much as 45-50 percent by changing bit design and operating conditions. This approach has been verified with North Sea data where the generated rock strength from the 12,25" section has been used as input to simulate the ROP and rotating time. These simulations compare well with the measurements of ROP, made in the two following wellbores drilled in the same field. Simulating ROP using drilling data from a well in a nearby field also gave promising comparisons. Introduction The DRilling OPtimzation Simulator (DROPS) is developed to reduce the cost of future wells based on a Geological Drilling Log (GDL), created from the data collected in a previous well drilled in the same area. The GDL is created using ROP models inverted to calculate rock compressive strength. The simulator has the capability of simulating any combination of operating conditions, bit designs, pull depths, hydraulics, WOB and RPM. The basic idea behind DROPS is to simulate the drilling operation prior to the actual drilling, and to find the optimum cost level. Simulations to verify the software (drill behinds) have been performed using actual field data from the North Sea, provided by Saga Petroleum ASA, well A and B. Data from well C, provided by Statoil, have also been used in the drill behind simulations. The simulated ROP results from the drill behind compares well with the results for actual measured ROP and cumulative rotating time, which are promising for further development and application of the method. Based on the comparison some cost optimizations for future wells in this region have also been performed. The cost reductions obtained indicate potential cost savings of 45-50 percent of total drilling cost per well, compared to the current industry practice in the area. By using this methodology in the planning process the most cost effective drilling program can be obtained.

Statoil operates the Troll Field in the Norwegian Sector of the North Sea and wished to run a deep sidetrack from the mother bore in a multilateral well that would exit through the 10-3/4-in. liner in the reservoir. The plan would have to address several new challenges, including an intelligent completion that would offer zonal isolation for four zones and dual pressure and temperature for all oil zones; these were not usual requirements for the standard multilateral wells in the field. Statoil had evaluated several zonal-isolation methods, and based on previous experience, they decided to use swellable packer technology. Since this would be the first intelligent-well completion in Troll field and the first ever for Statoil using feed-through swellable packers, a full scale test to qualify the technology was required. Swelling and differential-pressure tests were initiated using oil from the Troll field. Testing revealed that this type of completion actually would exceed the necessary requirements. The lower completion was designed with 7-in. inflow-control-device (ICD) mesh screens and three openhole swellable packers to isolate the reservoir into three separate oil zones and to separate the gas cap. The inner completion string was designed with three dual gauges, three 3-1/2-in. feed-through swellable packers, three 3-1/2-in. hydraulic flow-control valves, and a hydraulically operated gas-lift valve below the production packer to allow natural gas lift. The installation was performed from a semi-submersible rig without an HSE incident and ahead of plan. The well was put on production shortly thereafter, and zonal isolation was confirmed by selective closure of the flow-control valves. The paper will discuss the swellable packer design, qualification testing, planning, installation, and the results of this intelligent completion, which was the first in the Troll Field.

This paper shows how using the Drilling Gptimization Simulator (DROPS) has been applied in the planning phase of two North Sea wells. Both the 12.25" and the 8.5" sections were optimized on Well #1 and the 12.25" section was optimized on Well #2. Geological Drilling Logs (GDLs) were generated from offset drilling data in the same field for both the two wells. Both wells with the different hole sections were simulated with the available bit types and designs. The optimum bit selection and the drilling parameters every meter for the hole-sections were optimized. The hydraulic limitations of the pump and the planned mud weight program were used to optimize the bit hydraulics in conjunction with the bit operating parameters, different pull depths and bit designs. The 12.25" sections showed savings potential of 72.4 percent on Well #1 compared to the last well drilled in the field. This included optimizing bit type, hydraulics, operating parameters and pull depths. Well #2 showed savings potential of 15 percent using oil based mud and 20 percent using water based mud compared to the two other wells drilled previously in the field with oil and water based mud respectively. It was concluded that Well #1 could save $ 1.3 million, while Well #2 was originally drilled close to optimum and only showed a potential savings of $ 0.3 million when using optimum drilling parameters. The optimization of the 8.5" section was more complex because of several coring intervals. The five full hole sections between the coring intervals were optimized. The five subsections were drilled through formations of different length and lithology. The bit designs, pull depths, number of bits, hydraulics and operating conditions were optimized for each section. In addition to optimization of the drilling parameters, simulations for reuse of bits were conducted to further cut the drilling costs. The cost savings on the 8.5" section for well#1 showed a maximum potential for saving varying from 23.4 to 78.8 percent for the different sections. From the simulations it can be concluded that the optimum drilling scenario of the 12.25" and 8.5" fitll hole sections for well #1 would reduce the drilling cost with more than $ 4.5 million. P. 161

The Troll Field is located approximately 80 km northwest of Bergen in the Norwegian Sector of the North Sea around 65 kilometers west of Kollsnes, and is operated by Statoil. The field is comprised of the main Troll East and Troll West structures in blocks 31/2, 31/3, 31/5 and 31/6. Although the field historically had produced large amounts of oil, it is now also a major gas producer, as it contains approximately 40% of total gas reserves on the Norwegian continental shelf. The gas reservoirs that are 1,400 meters below sea level are expected to produce for at least another 70 years. Statoil, wishing to run a deep sidetrack from the mother bore of a multilateral well, decided to evaluate several zonal isolation methods and to combine this with intelligent well completion technology. Since this would be a "first time" Statoil Troll field deep sidetrack from the mother bore in a multilateral well application, regardless of the technology selected, a full scale test to qualify the technology for the application would be required. After evaluating several zonal-isolation methods, and their previous experiences with isolation concepts, Statoil decided to use a combination of intelligent well completion design with feed-through swellable packer technology. This combination concept would not only be the first intelligent well completion of its kind in the Troll field, it would also be the first ever Statoil use of feed-through swellable packers. Swelling and differential pressure tests were initiated using oil from the Troll field. The testing revealed that this type of completion exceeded the sought-after requirements for the project. This well design was then approved and installed on a semi-submersible rig without any HSE incidents and ahead of plan. The well was put on production shortly thereafter, and zonal isolation was confirmed by selective closure of the flow control valves. Additionally a second nearly identical completion well design was installed in May 2013. The paper will discuss the swellable packer design, qualification testing, planning, installation, and the results of the first intelligent completion with feed-through zonal isolation on the Troll Field.