|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
Altemeemi, Bashayer (KOC) | Gonzalez, Fabio A (BP Kuwait) | Gonzalez, Doris L (BP America) | Jassim, Sara (KOC) | Snasiri, Fatemah (KOC) | Al-Nasheet, Anwar (KOC) | Al-Mansour, Yousef (KOC) | Ali, Abdullah (NAPESCO) | Sheikh, Bilal (NAPESCO)
Asphaltenes flow in equilibrium with the liquid phase as other components of the produced hydrocarbon. If asphaltenes are in solution during production, there are not negative impact to well productivity. However, asphaltenes could precipitate as pressure, temperature and composition change. If precipitated, due to pressure decrease, asphaltene could deposit as a solid phase in the formation rock near wellbore becoming an obstruction to flow and inducing formation damage. Skin due to asphaltene deposition near wellbore was confirmed in several wells of a carbonate reservoir. Asphaltene deposition was also observed in the production tubing. The objective of this work is to investigate the main variables affecting asphaltene deposition in the Magwa-Marrat field is South East Kuwait and develop a technique to manage and/or decrease formation damage due to this solid deposition phenomena. In order to estimate the skin value and predict the location of any impairment to production, a pressure gauge was set at 1,000 ft above the top of the perforations and the well was equipped with a permanent multiphase meter device. A series of pressure buildup tests and multi-rate tests were run to disseminate Darcy skin from non-Darcy skin. Pressure transient analysis (PTA) delivered total abnormal pressure losses from the formation near wellbore to the gauge location, while multi-rate tests (MRT) allowed to investigate rate dependent skin. Well tests at different rates were also run to investigate the relationship between fluid velocity and asphaltene deposition. Once the elements of total skin were split into Darcy skin and Non-Darcy skin, a tubing clean-out and a stimulation job were designed and implemented to eliminate the asphaltene deposits and remove the damage. Total skin was reduced from +30 to −3.5 and productivity index was increased by a factor greater than ten (10). The production rate to mitigate asphaltene deposition was successfully determined. The well has been on production for about 1 year without developing any additional damage and without further deposition of asphaltene in the production tubing as the well has been flown above the minimum flow velocity that would allow asphaltene deposition. A combination of well intervention combined with determination of operating conditions have been developed to successfully produced asphaltenic hydrocarbons at flowing bottom hole pressure (FBHP) below asphaltene onset pressure (AOP). This methodology has been successfully implemented. If the liquid velocity is high enough to carry precipitated asphaltene out, solid deposits are not observed and there is not harm to productivity. The technique has worked for a case where reservoir pressure has been depleted below asphaltene onset pressure (AOP). This is a fundamental change in the globally applied industry approach that urges to produce asphaltenic hydrocarbons at FBHP above AOP.
Al-Obaidli, Asmaa (KOC) | Al-Nasheet, Anwar (KOC) | Snasiri, Fatemah (KOC) | Al-Shammari, Obaid (KOC) | Al-Shammari, Asrar (KOC) | Sinha, Satyendra (KOC) | Amjad, Yaser Muhammad (Schlumberger) | Gonzalez, Doris (BP) | Gonzalez, Fabio (BP)
The Magwa-Marrat field started production early 1984 with an initial reservoir pressure of 9,600 psia Thirty-six (36) producer wells have been drilled until now. By 1999, when the field had accumulated ~92 MMSTB of produced oil and the reservoir pressure had declined to ~8000 psia, the field was shut-in until late 2003 due to concerns on asphaltene deposition in the reservoir that could cause irreversible damage and total recovery losses. The field was restarted in 2003 an it has been in production since then. By April 2018 the field had produced 220 MMSTBO, with the average reservoir pressure declined to 6,400 psia. As crude oil has been produced and the energy of the reservoir has depleted, the equilibrium of its fluid components has been disturbed and asphaltenes have precipitated out of the liquid phase and deposited in the production tubing. There is a concern that the reservoir will encounter asphaltene problems as the reservoir pressure drops further. The objective of this manuscript is to present the process to understand the reservoir fluids behavior as it relates to asphaltenes issues and develop a work frame to recognize and mitigate the risk of plugging the reservoir rock due to asphaltenes deposition with the end purpose of maximizing recovery while producing at the maximum field potential
Data acquired during more than 30 years have been integrated and analyzed including 22 AOP measurements using gravimetric and solid detection system techniques, 17 PVT lab reports, 1 core- flooding study and 1 permeability/wettability study.
Despite the wide range of AOP measured in different labs, it was possible to determine that the AOP for the Magwa-Marrat fluid is 5,600 ±500 psia and the saturation pressure is 3,200 ±200 psia.
Results of this fluids review study indicates that it might be possible to deplete the reservoir pressure below the AOP while producing at high rates. Additional field testing and lab research have been proposed to 1) establish an adequate operating envelop for each well to optimize production and mitigate asphaltene deposition in the tubing to decrease downtime due to coiled tubing cleanouts which will reduce OPEX, 2) Support determination of a suitable reservoir pressure depletion to minimize CAPEX by implementing a pressure support project at an optimum reservoir pressure, and 3) Establish an appropriate field development strategy to produce the field at its maximum potential without jeopardizing the health of the reservoir while optimizing ultimate recovery
Marrat reservoir in Magwa field in Greater Burgan, Kuwait is a carbonate heterogeneous reservoir belonging to Lower Jurassic. Marrat is classified as a tight reservoir with an average permeability of 17md and contains light oil of 38deg API. The formation is around 2400ft thick divided in three sub layers namely Upper, Middle and Lower Marrat. Middle Marrat is the main oil reservoir which has been perforated and tested to be oil producing in almost all the 30 drilled wells. The reservoir consists of Grainstones, Packstones, Wackstones and Mudstones. Marrat was put on production in 1984 and solution gas drive is the main drive mechanism. The reservoir is naturally depleted due to limited water aquifer. The reservoir pressure declined 17% from the initial reservoir pressure within 15 years to current pressure of around 8000 PSI. Field Development Plan envisages pattern and peripheral water injection and facilities development for water injection is planned. Asphaltene flocculation at wellbore, tubular and surface facilities has been recognized as a severe problem. One of the options to avoid asphaltene problems in the reservoir, including the near wellbore region, is to maintain reservoir pressure and flowing BHPs above the asphaltene onset pressure (AOP) of ~ 6500 PSI.
Formation fluid contains around 1000 ppm of H2S and 4% CO2 which throws a corrosive environment also to tackle with. The well head equipment with present metallurgy often leaks on pressure tests and there is a plan to replace during future work over jobs. Coil Tubing Cleaning of tubular with light aromatics is a routine operation to maintain production from wells.
Increased demand of oil necessitated safely increasing oil production from Marrat reservoir. Keeping in view the challenges, a multi-disciplinary team was formulated to look into all possibilities. Focus was on Acid Fracturing Technique which had proved to be successful in the past. However with advancement in acidizing and diversion chemicals, the new system was field trialed.
This paper will discuss the process to select the wells and successful attempt of acid fracturing in two wells to tap oil from new areas.