Oman completion strategies continue to evolve as more cased horizontal wells are completed. These wells must be perforated and, for the best production performance, should be completed underbalance avoiding any kill as part of the process. Early wells were perforated using coiled tubing with mechanical sealed ballistic connector 1 to shoot in underbalance conditions and retrieve the gun assembly without having to kill the well. While the use of Coiled Tubing is a very effective deployment method, the extreme trajectory of some wells requires that fluids to ease drag friction be pumped as part of the deployment process. These friction reducing fluids may damage the perforations resulting in poor productivity.A new wireline tractor conveyance technology designed for the harsh, high shock application of perforating has been used to perforate a long horizontal well section in underbalance conditions. Detailed pre-job planning and modeling was carried out to ensure the job could be executed as desired. Also the "lessons learned" gained in a previous attempt to use this technology helped improve the delivery efficiency. The guns were deployed and retrieved under controlled conditions minimizing any perforation damage in addition to significantly reducing the running times compared to other conveyance methods used in previous wells.Eighteen successful tractor runs were made deploying up to 18.9 m of 2 7/8" OD perforation guns per run shooting 253m of perforation interval. Operating time was reduced significantly compared to previous perforating operations and no additional formation damage was done to the perforations as part of the process. Subsequent well productivity was better than expected.The success of this operation opens up a wide range of applications for perforating or other heavy duty and high shock applications for this tractor technology. In the future different deployment technologies can be combined with the tractor for conveyance to push even longer gun strings into highly deviated wells in "live well" conditions further improving completion efficiency.This paper will review the technical considerations and the detailed planning exercise that is required for a successful tractor perforating job as well as the operational requirements to minimize nonproductive time (NPT). This in turn will improve job planning and the likelyhood of operational success for future perforating jobs in this complex operating environment.

Due to high global demand, easy oil production is no longer sufficient to meet the continuous requirements. Extracting oil by using enhanced recovery methods or from difficult environments poses many challenges that differ from one field or formation to another. Ultrahigh-strength formations present a particularly difficult environment. In addition to posing drilling challenges, such formations introduce significant challenges to completion operations—particularly perforating and hydraulic fracturing, which represent the critical final steps in establishing formation-wellbore communication. A key perforating parameter is the perforation tunnel depth of penetration (DoP). A new paradigm of DoP modeling relies on shaped charge characterization in the laboratory under a range of rock strength and stress; however, most available data are for rock strength or unconfined compressive strength (UCS) values of less than 18,000 psi. Therefore, uncertainty exists regarding DoP in some Oman formations in which UCS varies from 20,000 to 55,000 psi. Two main phenomena need to be verified. First, because penetration is inversely proportional to UCS, extrapolation of the existing shaped charge performance data suggests that the penetration will be close to zero at this extreme rock strength. Second, characterization of the shaped charges under this new paradigm shows that a shaped charge that performs better in a weaker rock may not necessarily perform better in stronger rocks. Therefore, tests are needed to identify the optimal charge(s) in these very strong rocks. With these objectives in mind, cores obtained from the ultrastrong Amin formation in Oman underwent laboratory testing. Performance results of a series of tests designed in general agreement with the procedures of the American Petroleum Institue Recommended Practice (API RP) 19B Section 2 exceeded expectation based on extrapolation of previously available laboratory data. These new data provide valuable calibration points for the penetration model in ultrahigh-strength rocks. This paper presents the methodology, results, and observations of this test program and discusses the way forward, which should add value to perforation performance not only in Oman, but also worldwide in ultrahigh-strength formations. Although previous studies have briefly addressed high-strength formations, this is the first known work that systematically evaluates perforator performance in ultrastrong formations.

West Lutong is a mature field with 8 rounds of field development campaigns and close to 40 years of production. Currently, only 50% of total strings are flowing. However, the idle wells could possibly access undeveloped marginal reserves in shallow reservoirs. These shallow reserves are located above top production packer as they were not previously included in initial completion due to historical sand problem Following West Lutong Full Field Review in 2006, presence of by passed potential reserves above top production packer were confirmed. Conventional workover rig to re-complete these potentials is not economically viable due to significant cost and complexity. An innovative, rigless "cement packer" approach, had been chosen for the pilot job in Well # A, while retaining necessary level of completion integrity. The proper placement of cement packer approach involves usage of hydrostatic sequence valve as choke manifold to prevent U tube effect. Numerous down hole problems such as wax, scale, sand and fish from insert string had been rectified using appropriate coiled tubing solutions. Conventional E-line perforation using high density shot gun and deep penetrating charges were then used. Well # A had been producing, under controlled condition, average 930 bopd without sand problem for 10 months since July 2008 with 1.10 MMstb reserves monetized. The total cost was only 10% of a conventional workover. This paper shares a detailed case study of Well # A in term of candidate's selection, reserves estimation, cement packer execution, lessons learnt, and future recommendations. It is evident that cement packer technology is feasible and economic for accessing by passed reserves above existing production packer. Introduction The West Lutong field was discovered by well WL-01 in 1966 and brought on production in mid 1968. It is located offshore Sarawak approximately 13Km North West (NW) of Miri in water depth of 70 -100 ft. The first discovery well was drilled in 1966 and a total of 4 additional wells were drilled thereafter to appraise the structure. Production started in 1968 from the four exploration/appraisal wells. Subsequently, there have been a total of 8 drilling/workover campaigns as depicted in Figure 1. Currently, only 50% of total strings are flowing. However, the idle wells could possibly access undeveloped marginal reserves in shallow reservoirs. The West Lutong reservoirs were deposited some 20–23 million years ago during Cycle V of the late Miocene in a lower coastal plain to coastal environment. Shore face deposits dominate the sequence, which also includes some channels and associated bar forms. Reservoir sands are loosely consolidated, fine to very fine and inter-bedded with layers of silts and clays. Average reservoir porosity ranges from 14 to 26 % with a field wide mean of 20%, permeabilities are in the order of 50 to 300 mD, average net-to-gross is 0.62 and net sand thickness is generally less than 30 ft, with most sands around 10 ft thick.

The offshore state of Sarawak in Malaysia contains many mature wells that were completed 20-30 years ago with dual-strings and multiple packers to exploit the many layers of sand packages. The wells that were designed to exploit the main sand packages are currently depleted and producing at high water cut. The operator is now considering ways of exploiting the smaller intermediate sand packages in these wells. In many cases, this requires oriented perforating through one completion string while avoiding shooting another completion string that is still producing. Oriented perforating using analog orienting devices that were previously deployed has many operational problems that on several occasions have led to abandoning jobs, and ultimately deferment of additional production. As such, this has led to many of these mature wells that require oriented perforating being left unexploited for many years. The arrival of a new digital orienting device is expected to open the path to better exploitation of the intermediate sand packages.This paper is a case of deployment of this device for PETRONAS Carigali in Sarawak, Malaysia which required collaboration with the service contractor at many stages, from planning and characterizing the device responses in various completion configurations in Sarawak, to writing standard operational procedure and contingency planning, and to real-time decision making during operation.The results of operation of this device on two wells in Sarawak are also presented, as is how the collaboration in the planning stages contributed to their successes.While the success paves the way for future exploitation of the intermediate sand packages for PETRONAS Carigali, the exercise also provides a reference for similar operations in other places, from the point of collaboration and technicality of the service itself. IntroductionThe offshore state of Sarawak in Malaysia contains many mature fields that were drilled 20-30 years ago. Most have many packets of sands and were completed with dual-strings, multiple packers, and sliding side doors (SSD) to avoid commingling different oil zone reservoirs. If all the sands were to be produced from the same well, that would require a very complex completion string, something that could be very expensive or would be limited by the availability of technologies at that time. Furthermore some of the sand packets are small in comparison with the main sands. As such, only the main sands were perforated and produced in an optimized completion string. Fig. 1 and Fig. 2 show two typical dual completion wells in the state of Sarawak.

Effective zonal isolation in wellbores with a challenging mud removal environment is well known to be very difficult to achieve. In wells at the technical limits of Non- Aqueous Fluid (NAF) removal prior to cement placement, cement bond quality and hydraulic isolation can be compromised by leaving channels behind the casing, which can result in several long-term well integrity issues. An Interactive Cementing System (ICS) is developed through special experimental methodologies to mitigate mud channeling issues and improve zonal isolation, by immediately interacting with any residual mud channels left in the well after cement is in place, hence reducing the permeability of mud channels and sealing off microannulus gaps. Casing centralization is considered to have the greatest influence on mud removal efficiency because it directly affects the flow movement on each side of the wellbore. Mud removal has been studied from numerical simulations, laboratory experiments, and field results, and these show that good mud removal can be achieved only when adequate casing standoff is achieved during cementation. In modern wells where there are many operational restrictions and limitations, especially in highly deviated and horizontal wellbores, final cement designs may not allow good casing standoff and thus not all of the best practices for effective mud removal can be applied. The objective of the innovative cement system is to have a design that interacts with residual mud in the annulus to "fix" the channels, thereby enhancing cement bond quality and zonal isolation. Two detailed case histories of the application of this technology in the development campaign showed visible improvement in cement bond logs using the ultrasonic imaging tool as compared to offset well that was cemented using a conventional cement system. After two successful implementations, the ICS was selected as the cement system of choice for wells with challenging mud removal.