In one Saudi Aramco offshore oil field, the formation fluids are being produced from different platforms and transported to one onshore gas-oil separation plant (GOSP) where the produced water is removed from the hydrocarbon stream. The produced water is injected back to highly permeable formations through disposal wells with no interruption. In this way, the water disposal system is an integral part of the hydrocarbon recovery system. A failure of one of the disposal wells could adversely affect oil production. Saudi Aramco petroleum engineers are placing more and more attention on water disposal wells as a higher volume of produced water from the increasing hydrocarbon production rates has to be disposed of continuously every day. The primary objective of surveillance on the disposal wells is to keep an extra disposal capacity for continuous oil production from the field and to precisely monitor the decline rate of the capacity of each disposal well. Areal sweep efficiency and pressure maintenance are not the surveillance scope for water disposal wells in our case. Few technical papers have been published that discuss the problems a water disposal system may have in a matured field and address issues such as surveillance of well performance and water quality, formation damage mechanisms, treatment and so forth. In this paper, the existing water disposal system in a matured offshore oilfield is briefly described and discussed with the surveillance of well performance and the quality disposal water, potential problems, and the evolution of the surveillance philosophy. The reasons why most disposal wells experienced severe injection decline are analyzed and discussed in detail. Historic treatments were summarized with actual outputs demonstrating" ineffective" treatments for the issues discussed. After several trial tests, one customized chemical treatment recipe was developed to effectively tackle the issues and actual well data is included showing the effectiveness of those treatments. A new surveillance strategy for better monitoring of well performance and the quality of "waste" fluid is also discussed in this paper. It can be concluded from our work that formation damage exists extensively in wastewater injection wells and that it greatly influences the performance of disposal wells. Any treatment for restoring the injection capacity of water disposal wells impaired by low quality water is expensive. Any successful treatment is rooted into the detailed analysis of the problems. Implementation of a proper surveillance program and appropriate processing of the injection fluid is also vitally important for wastewater management.

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Over the last decade, many permanent downhole pressure and temperature gauges (PDG), also called permanent downhole monitoring systems (PDHMS), have been installed globally in many oilfields. One primary objective of installing permanent downhole gauges in a wellbore is to avoid field trips with a wireline unit for pressure surveys. Additionally the system can turn any well "shut-in" time into a valuable opportunity for both a pressure survey and a build-up testing, significantly improving the reservoir surveillance frequency. Only a few authors have conducted a systematic analysis and explored the potential application of a PDHMS system. This paper briefly describes the elements of a typical PDHMS monitoring system. A detailed systematic analysis is presented for the first time, including factors affecting the application of such a system. Our analysis reveals that the accuracy of the pressure gauges, gauge installation, depth and the distance between the two pressure gauges have a significant impact on the application of a PDHMS system. Improperly choosing the accuracy of pressure gauges, randomly placing the pressure gauges in a wellbore, or improperly setting a distance between two pressure gauges could result in little benefits from such practice. The analysis presented in this paper enables petroleum engineers to make the sound engineering decisions during the planning of PDHMS installation.Our study presented in this paper extensively includes an investigation of the specific requirements of such a system in different types of wells (producers and injectors) and explores their potential applications. This study extends the application of a PDHMS system to a new horizon in terms of production optimization and reservoir surveillance. Also presented in this paper are some cases showing how real time PDHMS data is utilized for continuously monitoring reservoir pressure changes, and optimizing both testing frequency and wellhead sampling requirements in a Saudi Arabia field.

Innovative Surface Jet Pump (Velocity SpoolTM) technology combined with novel compact separation was tested at a remote onshore wellhead location to see if it could increase multi-phase production from low pressure oil wells that were already producing and revive wells that were backed out/not flowing. The technology was mounted on the surface, not downhole and avoided well intervention, The Surface Jet Pump (SJP) is a passive device which utilises often wasted fluid energy (via choke) from a high pressure (HP) well to reduce the back-pressure of a low pressure (LP) well and boost its’ flow to the production manifold. In multi-phase oil applications where there can be significant amount of gas present, a compact in-line separator (called I-Sep) is installed upstream of the SJP to bulk separate the gas and liquid fluids and allow the liquid motive fluid to be directed to the SJP. For this trial, one of Caltec's patented SJP multiphase skids was installed at an onshore wellhead location and connected to existing HP and LP wells. Production from both wells was diverted to the SJP to test its effectiveness. The trial tests lasted 3 months. Results from the first set of tests showed that the SJP boosted production from a multiphase LP well that was already flowing by an additional average of 380 bbls/d with a corresponding wellhead pressure reduction of 45 psi. Results from the second set of tests showed that the SJP revived a dead well that had not been flowing since 2004 and made it flow at an average rate of 1092 bbl/d with a backpressure pressure reduction ranging from 54 to 27 psi. Prior to the trial, several attempts had been made to bring this dead well back into production using other methods but these were not successful. The results showed conclusively that the SJP was very effective in boosting production from LP oil wells. The production gain was achieved by lowering the FHWP of the well and the amount of gain was dependent on the productivity index of the well. The advantages that the SJP offers over any conventional technologies such as Multi-phase pumps and ESPs are several: it is tolerant to variations in flow conditions, gas volume fractions (GVF) and associated slugging (without affecting performance), it is surface mounted (so well intervention is not required), low cost, easy to deploy, has no moving parts, consumes zero fuel gas/electrical power and uses already available surplus energy. This paper reports the trial results and discusses the use of Surface Jet Pumps as an alternative to other boosting methods for oil production. The design and operational criteria of the SJP are also highlighted.

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