A few oil wells in a Saudi Arabian field have shown significant oil productivity decline in recent years. A few of them have ‘died’ prematurely while others have become intermittent producers. It has been noticed that the oil productivity decline is aggravated with water encroachment. The oil productivity decline has come about with relatively low water rates and without any significant drop in reservoir pressure. These wells have low productivity index (PI) resulting in relatively low flowing bottom hole pressures (FBHP). This paper presents the results of an investigative case study to determine the causes of productivity decline in these wells. A multi-disciplinary team was set up with engineers and scientists from reservoir management, production engineering and the R&D Center for the investigative study. The team focused on multiple aspects including reservoir and production engineering, as well as a comprehensive laboratory and field investigation. The results of this study indicate that one of the main causes of productivity decline in these wells is related to asphaltene precipitation and the subsequent formation of tight emulsions downhole. The emulsions block the pore throats and cause formation damage leading to productivity decline. Another factor that further aggravates the productivity of these wells is poor rock quality in the area. Possible causes of formation damage due to inorganic scaling, and leakage and mixing of gas from a deeper reservoir have been eliminated. Well test analyses on some of the affected wells shows the formation damage mechanism in the affected area is further aggravated by poor reservoir rock quality. The time-lapse pressure transient analysis also indicates a deterioration of skin and productivity with time. Based on these findings a special solvent treatment was recommended and designed as a pilot trial for one of the dead wells. The treatment included squeezing xylene and demulsifier to dissolve the asphaltenes and break the tight emulsions around the wellbore area. The treatment resulted in only a slight improvement in the productivity index and the well died after a few days. Currently a stimulation treatment with acid and demulsifier is being implemented in selected wells. The results of the field trials will be described in the paper. Introduction Several wells in the northwestern part of a Saudi Arabian field have shown productivity decline in recent years. A few of them have died prematurely at relatively low watercuts, some as low as 25%, which is atypical behavior for wells in the area. It has been noticed that the oil productivity decline is aggravated when wells become wet. The oil productivity decline has come about with water rates remaining mostly stable and without any significant drop in reservoir pressure. A location map of affected wells is shown in Figure 1. Oil and water production rates are plotted in Figures 2–4 for three affected wells. The oil production rates declined from ~10–12,000 BPD to less than 1,000 BPD over a period of approximately 4–5 years. Water rates remain generally low at less than 2000 MBD. It can also be observed that the oil rate decline is substantial as soon as water breaks through in the well. This study was initiated with the objective of finding the causes of productivity decline in these wells and finding effective ways to mitigate the problem. A multi-disciplinary team was set up with members from reservoir and production engineering and the R&D Center. Several potential causes of productivity decline in these wells were investigated including the precipitation of asphaltenes, emulsion blocking, mixing of hydrocarbons from a deeper reservoir, inorganic scale precipitation, aquifer brine and injected water compatibility, regional geology including rock quality, drilling fluid damage, and distance of wells from the Gas Oil Separation Plant (GOSP).

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 year marks the sixth year anniversary of the birth of the Maximum Reservoir Contact (MRC) wells in Saudi Aramco. The outstanding performance of 99 MRC wells drilled to date in different fields reflects the impact of MRC wells on improving well performance, enhancing recovery and reducing unit development costs. In view of this performance, the use of this technology will continue to be on the rise. This paper will highlight the drivers, selection criteria, and lessons-learned from the MRC wells. It will further highlight cases of how MRC wells became the cornerstone in optimizing the development of tight reservoirs and in re-engineering mature ones. In addition, the paper will highlight the impact of MRC wells on rate sustainability and on increasing off-take levels by up to five times when compared to vertical and single lateral well completions. MRC wells not only targeted new development wells, but also extended to workover programs where low performer and dead wells were converted to MRCs. Results were phenomenal in terms of improving well productivity and delaying water and gas breakthroughs-thereby improving sweep. Introduction An MRC well is defined as a well having an aggregate reservoir contact in excess of 5 km, through a single or multi-lateral configuration. The MRC well concept was developed to further improve well productivity and thereby lower drawdown pressures resulting in higher well potential and lower development costs. MRC wells have been mainly deployed, in Saudi Aramco, in reservoirs with low to medium rock permeability, and relatively thin oil columns. The first deployment of MRC technology took place in 2002. MRC wells have primarily been implemented in three fields: Shaybah, Haradh and Abqaiq fields. By year-end 2007, 99 MRC wells were completed in Saudi Aramco. Several publications were issued on this topic highlighting the succession of MRC wells in Saudi Aramco 1–7. Figure 1 illustrates the growth of MRC wells since 2002. The use of this technology will continue to be on the rise reaching several hundred MRC wells in the next four years. 31320337599200220032004200520062007Cumulative MRC Wells Year Results from the three fields have proven that MRC wells have significantly improved reservoir and well performance, minimized or eliminated water and gas production, and reduced development cost. The first MRC well drilled in Shaybah field was a tri-lateral well with a reservoir contact of 8.5 km. Initially, the MRC wells in Shaybah field were completed through open-hole completion. The MRC concept was not limited to new wells, it has also revolutionized the workover practices to maximize the value of existing wells (i.e., weak or dead conventional or single lateral wells). The effectiveness of MRC wells depends on the proper planning, design and placement of the laterals. This paper will capture the drivers, selection criteria and lessons-learned over the past six years of MRC implementation.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe last decade has been marked by the emergence of intelligent field technologies. Many E&P companies have moved from the piloting and trial-testing mode towards strategic implementation demonstrating that these technologies have shown their capabilities. While the current deployment of these technologies represents only a small fraction of the overall installation, the trend is indicative of the shifting of attitudes and preferences within companies. Among those companies, Saudi Aramco has deployed fit-for-purpose technologies such as intelligent wells equipped with multiple downhole valves, as part of its best-in-class practices (Figure1). Continuous assessment of these technologies is important to provide reassurance on their values.The resulting performance of this technology is a function of multiple factors spanning from reservoir parameters, completion schemes to surface infrastructure. Understanding and assessing the impact of these factors is complex due to the wide variation of variables.This article summarizes the lessons learned from more than one hundred deployments in wells equipped with multiple downhole valves. These lessons illustrate the advantages of these applications and should provide insight for improved performance. As there is no "one size fits all," then proper design should be emphasized for maximum effectiveness.

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