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This paper presents two case studies that evaluate the impact of the Linearized Inflow Control Device (LICD) on horizontal wells performance in a Saudi Aramco giant carbonate field. Linearized Inflow Control Devices regulate inflow by diverting production either through spiral channel or through pre-determined choked ports. The net effect is to restrict high productivity segments while increasing flow in the low productivity segments. LICDs are being utilized as part of an initiative to use custom-fit technologies to optimize horizontal well performance, thereby improving sweep and recovery efficiency. The objectives of drilling horizontal wells in this field are to prolong dry oil production, increase reservoir drainage and efficiently sweep oil beneath the gas caps and/or behind the flood front. Horizontal wells, however, have been faced with the challenge of producing reservoir fluids through non-uniform inflow from reservoir heterogeneities/pressure variations along laterals, presence of fractured zones and frictional effects along the wellbore. The non-uniform inflow promotes early water/gas break-through, leading to short-lived wells and unfavorable sweep. As a solution to this challenge, LICDs have been installed in selective horizontal wells. Results to date show remarkable improvement in well performance, where gains in oil production with controlled water production has been achieved. Long-term reservoir simulation results also showed considerable recovery increase in the linearized case over the non-linearized case. This paper presents the evaluation and results of linearized ICD technology, and how it became a game changer in this field development. Introduction The benefits of horizontal wells were recognized in the late 1970's, although such type of wells was first drilled in the 1940s or earlier. It was, however, advancements in downhole motors, drill fluids and measurement-while-drilling (MWD) equipment that allowed delivery of low-cost horizontal boreholes. In the early 1990s, drilling of horizontal wells became a common place and proved to be a milestone in the development of challenging (mature, thin oil rim, tight and heavy oil) reservoirs. Further advancements in drilling and completion technologies resulted in making extra-long or multi-lateral boreholes becoming viable. Smart and complex downhole equipment has further enhanced performance of such wells. LICD systems, which are simple and reliable downhole devices, proved to be effective technology in promoting performance of horizontal wells 1,2. Description The case study wells, Well-A, Well-B are producers drilled in a giant field, with production history of more than 50 years located in Saudi Arabia. The field is a composite Jurassic carbonate anticline, with several gently dipping crestal regions containing undersaturated Arabian light grade oil. It was initially produced under depletion drive followed by a 20-year period of partial pressure maintenance, utilizing produced gas as well as gravity water injection. Full pressure maintenance was initiated in the 1980's by peripheral power water injection. Development and infill drilling is still underway tapping oil, reserves both underneath the two small size injection-induced gas-caps and behind the flood front areas utilizing horizontal well technology.

This paper presents a study on a six-year water management strategy in North 'Ain Dar to reduce water production, prolong well life and enhance oil recovery. This field has been under peripheral injection for more than thirty years. Three strategies were implemented during the past five years to achieve optimal water management:production optimization,rigless water shutoff jobs, andhorizontal drilling. The success of these strategies can be attributed to a full understanding of the drive mechanisms that control fluid transport in the reservoir. This paper presents these mechanisms and their impact on water management strategies. The effectiveness of these strategies have been evaluated and supported by field data. Horizontal drilling and rigless water shut-off proved to be effective techniques to control water production and enhance recovery in this gravity dominated system. Since 1999, production optimization has also played a significant role in controlling the water production and maintaining a constant water cut. Introduction Field History: This field represents one of the most mature parts of Ghawar. It was discovered in 1948 and regular oil production began in 1951. The oil grade is Arabian light with an average API of 34º and a solution GOR (Gas-Oil-Ratio) of 550 SCF/STB. This field has a modest natural water drive support, thus peripheral water injection was initiated to provide full pressure maintenance in 1968. Initially, water injection was conducted by gravity water injection. This was replaced by power water injection to provide flexibility in controlling the waterflood front propagation. Reservoir Geology: This field has more than four oil and gas bearing reservoirs. The focus of this study is the Arab-D reservoir, which is the most prolific oil bearing formation. In this field, Arab-D is characterized as a folded anticline consisting primary of Jurassic carbonate. The diagenetic effects on the Arab-D sediments are minimal and the calcite cementation is rare and barely coats grains surface.[1] Matrix porosity and permeability averaged 25% and 600md, respectively. Historical Performance: Fig. 1 shows the overall production history of the field. The field has maintained the capability of producing at a high rate for almost 50 years except for the mid-eighties due to low demand. The water production started in the late seventies and increased moderately to 42% at the beginning of year 2005. The main focus of this paper is the last six years. Since 1999, the oil and water production, water injection, and reservoir pressure were kept effectively constant as shown in Fig. 2. This sound behavior is a result of active strategies taken during the subject period. Those strategies are in alignment with the rigorous logic of reservoir management tenets practiced by Saudi Aramco. As defined by Saleri[2], the tenets include thoughts, principles, processes and practices by which the field is managed. Reservoir Surveillance & Fluid Mechanics The field has been under a yearly comprehensive surveillance plan. This plan dictates full areal coverage for logs and static bottom-hole pressure (SBHP) surveys as shown in Figs. 3 and 4. Logs, such as Formation Analysis Log (FAL), Production Logging Tool (PLT), Carbon/Oxygen (C/O), and Thermal Decay Time (TDT), are required to ensure vertical sweep conformance and infer sweep mechanism. SBHPs are required to ensure that the reservoir pressure is above the bubble point pressure. In addition, a strategic surveillance materplan (SSM) has been initiated to further ensure accurate determination of remaining oil saturation (ROS) and pressure. The SSM will be discussed later in this paper. It is imperative to mention that the water management strategies were not on the expense of sweep conformance. Areal sweep conformance can be easily demonstrated by the even movement of the flood-front as shown in Fig. 5. While vertical conformance can be supported by FAL results for wells drilled behind the flood front. Fig. 6 shows the FAL results for A1 and 2, where both wells exhibit an excellent vertical conformance.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe trial test of Wireline Retrievable Side Pocket Surface Read-Out Permanent Downhole Monitoring System (SPSRO-PDHMS) was successfully conducted in a newly drilled well in a giant oil field in Saudi Arabia. In the wireline retrievable PDHMS system, the downhole gauges sit in a side pocket mandrel; if the downhole gauges malfunction, they can be retrieved and replaced easily with wireline. Conventionally these gauges are run on tubing and in case of gauge failure, a workover rig is required to replace the malfunctioning gauge (there are 6 wells with malfunctioned/failed gauges in the operated field). The WL retrievable option would eliminate the $500,000 rig cost per well to replace malfunctioning or damaged gauges.

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractThin reservoirs of a few feet in thickness present a clear challenge to well placement. Drilling out of the target is a real possibility, and plugging back and reentry can be extremely difficult. Clearly, the best solution is to avoid exiting the target reservoir by detecting approaching boundaries as early as possible and by remaining at an optimal distance from the boundaries. This practice is known as "proactive geosteering." In recent developments, wave resistivity LWD and azimuthal wave resistivity sensors have been shown to effectively facilitate proactive geosteering. Their abilities to scan laterally several feet, up to more than 10 ft, around the wellbore and to identify the relative azimuth of approaching boundaries have been instrumental in recent successes.The challenge posed by the subject reservoir in this study is the combination of the thinness of the reservoir, approximately 3 ft, and the high resistive environments of the boundary, zero-porosity anhydrite formations, as well as the oil reservoir containing a low porosity dolomite layer. The challenge was met by carefully selecting the most appropriate measurements to send to the surface, interpreting them in real time, and using multi-boundary inversion. A series of pre-well simulations were run using offset wells. The simulation results showed that for the most likely scenario, shallow azimuthal wave resistivity curves and images provided the highest sensitivity to the approaching boundary. Medium and deep resistivity curves were less active and of lower resolution, but they contributed to the inversion for dual boundaries. Newly generated high resolution electric and density reservoir imaging and petrophysical logs were also interpreted in real time to assess the relative dip and provide finer control of the well angle. They helped to verify that the well remained within the reservoir through nearly its entire span, i.e., that the well was successfully placed with a high net-to-gross in a very thin reservoir in resistive environments.