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Collaborating Authors
Production & Reserves Allocation Using a Molar Equation in Gas Condensate Fractured Reservoir Without PSP Survey
Shahid, Muhammad Hasan (Reservoir Engineering Department Ocean Pakistan Limited Islamabad Pakistan) | Akhtar, Muhammad Saeed (Reservoir Engineering Department Ocean Pakistan Limited Islamabad Pakistan) | Shakeel, Mariam (Reservoir Engineering Department Ocean Pakistan Limited Islamabad Pakistan)
Abstract The Ratana Field is a gas condensate field located in the Potwar Basin of Pakistan, discovered in 1990. The field comprises several stacked reservoirs in a thrusted anticlinal fold with two main reservoir compartments, an eastern and a western, which are separated by the main thrusts, but appear to be in pressure continuity through a fracture network. Ratana-2 was the first well drilled in the western compartment which came on production from the Paleocene Patala Formation limestone reservoir and is a major producer in the field. Ratana-2 was subsequently deepened to the Jurassic Datta Formation but because of a stuck drill string in the hole all penetrated reservoirs (Chorgali/Sakesar, Patala, Lockhart and Datta) have been open to flow since November 2009. Well interventions are not therefore possible in Ratana-2 and production and reserves allocation based on limited dynamic data are thus very challenging. Surface-based parameters including water and gas composition analysis, wellhead shut-in pressures, surface production rates and other relevant data were used to perform production and reserves allocation by using a molar equation. The results of the molar equation predictions were cross-checked with the data from nearby well Ratana-4 which is also producing commingled from Paleocene and Jurassic age reservoirs since November 2015. Production logging surveys were acquired twice in over a period of six months and were consistent with the molar equation-derived formation-wise production allocation. Subsequently, the molar equation was used on the available surface data of Ratana-2 for the formation-wise production and reserves allocation and indicates for the first time that the Lockhart Formation as is a contributing reservoir in the Ratana Field and enabling the Lockhart Formation reserves to be booked after seven years of production.
- Asia > Pakistan > Upper Indus Basin > Potwar Basin (0.99)
- Asia > Pakistan > Punjab > Chakwal District > Upper Indus Basin > Potwar Basin > Wargal Formation (0.99)
- Asia > Pakistan > Khyber Pakhtunkhwa > Karak District > Lockhart Formation (0.99)
Abstract The eastern Potwar region represents the most strongly deformed part of the Potwar fold & thrust belt, with large low angle detachment faults accommodating more shortening than elsewhere in the Potwar fold-and-thrust belt. The tectonic framework of the eastern Potwar region is largely controlled by the Salt Range & Domeli thrusts forward thrust systems, and the Dil-jabba & Domeli backthrusts. To constrain the 3D geometry of thrusts in the eastern Potwar region, we used the interpretation of data from 3-D and 2-D seismic and a series of structural cross sections. On the basis of these data, we developed a 3D model of the major fault planes as well as the basement surface underneath the eastern and southeastern Potwar region. 2D structural restoration was used to understand the pre-deformation phase of the structures. The results of this work illustrate that the foreland fold & thrust belt of eastern Potwar comprises classical imbricate thrusts, pop-up structures, and a regional triangle zone. The geometry and kinematics of thin-skinned deformation in the fold-and-thrust belt appear to have been controlled by basement-involved horst & graben. Evidence from the Salt Range implies that the structures formed during two main episodes of deformation: โฅ5 Ma normal faulting, and โค2.5 Ma thrusting. During the latter, deformation in the Potwar Basin and Salt Range area has been detached from the underlying basement along a continuous decollement within Precambrian Salt. The eastern Potwar region is an important oil & gas producing area, with hydrocarbon production from late Cambrian, Permian, and Eocene rocks. More than 50 wells have been drilled, which produced several million barrels of oil & billions of cubic feet of gas. The integrated three-dimensional structural model presented here will be contribute to a better quantitative understanding of the structural complexities in this region.
- Phanerozoic > Cenozoic > Paleogene (0.51)
- Phanerozoic > Cenozoic > Neogene (0.49)
- Phanerozoic > Paleozoic > Cambrian (0.48)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (1.00)
- Geology > Structural Geology > Fault > Dip-Slip Fault > Reverse Fault > Thrust Fault (0.50)
- Asia > Pakistan > Punjab > Rajian Field (0.99)
- Asia > Pakistan > Punjab > Kal Field (0.99)
- Asia > Pakistan > Punjab > Chakwal District > Upper Indus Basin > Potwar Basin > Sakesar Formation (0.99)
- (2 more...)
Unlocking Recovery Potential in a Mature Clastic Oil-Rim Reservoir Using an Integrated Reservoir Simulation Model: A Case Study of the Eastern Potwar Basin, Pakistan
Abrar, Saad Bin (Pakistan Petroleum Limited, Karachi, Pakistan) | Hashmi, Syed Shariq Ali (Pakistan Petroleum Limited, Karachi, Pakistan) | Sarmad, Muhammad (Pakistan Petroleum Limited, Karachi, Pakistan) | Siddiqui, Majid Najeeb (Pakistan Petroleum Limited, Karachi, Pakistan) | Aziz, Tariq (Pakistan Petroleum Limited, Karachi, Pakistan) | Sardar, Naeem (Pakistan Petroleum Limited, Karachi, Pakistan)
Abstract This paper presents a case study of Field Sigma, a large gas condensate field in Pakistan. Sigma comprises two primary sandstone reservoir formations, X and Y, where an oil rim was discovered during the late field life. A re-development plan utilizing an integrated reservoir simulation model was formulated to enhance oil production from the oil rim beneath a gas cap. The key challenges faced included reservoir pressure depletion, reservoir heterogeneity, complex fault geometry, and fluid contact uncertainty. The study aims to introduce a novel concept for optimizing oil production from the oil rim reservoir through an integrated reservoir study. In this study, an independent seismic interpretation was conducted on the most recent 3D seismic data, focusing on mapping the major faults that impact the static/dynamic reservoir model and evaluating the transmissibility of the mapped faults iteratively during the history-matching phase. A comprehensive petrophysical study was conducted to calculate various petrophysical parameters on a field scale, providing an updated and consistent analysis that minimized uncertainties from the previous interpretations. Field Sigma has a complex anticline structure with intricate fault geometries and thrust sections. Thus, the static model's structural grid was created using the Volume-Based Modelling (VBM) method, chosen over Corner Point Gridding to represent the complex nature of the field's structure accurately. The reservoir engineering data was thoroughly analyzed and incorporated into a dynamic simulation model. The history-matched, compositional model was used to generate production forecasts. From the various evaluated well locations, Eight economically favorable infill and appraisal sites were identified, with 5 in the Southeastern compartment and 3 in the sub-thrust area of the Northeastern compartment. To appraise the Free Water Level (FWL), Sigma-5 was proposed as an appraisal well in the Southeasternern compartment and after achieving the appraisal objective, in case of water production, the well had the option to sidetrack in an up-dip location. The infill wells Sigma-6,7 and 9 were proposed between Sigma-3 & 4 to drain the remaining hydrocarbon volumes and were considered comparatively less risky as compared to the other wells. However, due to the limited dynamic data, there exists uncertainty in the reservoir connectivity and there is a possibility of encountering further depleted pressures as compared to the simulated pressures. The appraisal well Sigma-8 is proposed to evaluate the eastern extent of the Southeastern compartment, however, this area has high-depth uncertainty and limited well control. All three wells identified in the Northeastern compartment target the Sub-thrust region and were considered high-risk wells. The paper emphasizes the crucial role of data integration from diverse sources in the re-development of a complex mature oil-rim brownfield through the combination of geological knowledge, reservoir-level petrophysical evaluation, incorporation of core data, production history, reservoir understanding, and critical data acquisition during the infill drilling, the project team gained the confidence to devise and execute successful re-development strategy. The iterative creation of robust static and dynamic models provides a valuable planning resource for future endeavors. The methodology outlined in the paper holds broad applicability to typical field developments, establishing it as a valuable industry practice.
- Asia > Pakistan (1.00)
- Asia > Middle East > UAE (0.28)
- Geology > Structural Geology > Fault (1.00)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.66)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.54)
Abstract The paper is based on experience gained during drilling in Potwar basin, on-shore Pakistan. The high cost of wells are primarily due to long drilling times resulting from extremely difficult drilling conditions, arising from abnormally high formation pressures. High pressure water inflows and loss circulations have led to premature abandonment of several wells on account of collapsed casing, bridging, caving, blowouts and cratering around the wells. The post-Eocene Siwalik formations in the Potwar basin are notorious for abnormally high formation pressures and reversal of pressure regimes in the pressures and reversal of pressure regimes in the sedimentary sequence. Pressures close to geostatic have been encountered at shallow depths. The aim of the paper is to take a close look at the mechanisms responsible for the generation of overpressure, identify problem areas, examine available options, keeping in view present drilling technology and equipment limitations, and finally recommend operational strategies to handle such situations. Planning of wells, monitoring of drilling Planning of wells, monitoring of drilling operations, selection of kick control procedures and wellbore integrity are considered to be critical factors for successful operations. Introduction Potwar Basin - Northern Pakistan (Fig. 1) is Potwar Basin - Northern Pakistan (Fig. 1) is situated in the east of river Indus. Since the turn of the century Potwar has been the scene of petroleum exploration and remained the only oil producing region of Pakistan until 1981. Oil production was established u early as in 1915 and to date a total of 16 fields have been discovered. Present production of oil in the region is above 30,000 barred production of oil in the region is above 30,000 barred per day. Exploratory drilling activity in this per day. Exploratory drilling activity in this basin, however, has remained at a slow pace, mainly due to difficult drilling conditions encountered in the Post-Eocene fresh water sediments. These sediments; Siwalik and Murrees (Nimadrics), arc of Miocene to Pliocene ages. High formation pressures, close to the geostatic have been encountered pressures, close to the geostatic have been encountered at shallow depths in some of the tightly folded and faulted structures in the eastern part of the basin. The excessive mud weights, required to control the water inflows, invariably resulted in fracturing of formations, causing severe loss of circulation. The alternating high and low pressure (thief) zones, and even more their unpredictability, further complicated the task of planning the exploratory or development wells. Advances in drilling technology, drilling fluids and kick control procedures have considerably helped in over-coming the drilling problems in Potwar. Possibility of discovering more petroleum Potwar. Possibility of discovering more petroleum reserves in sediments of Eocene to Cambrian ages still-exists in Potwar. Better understanding of abnormal formation pressures, improvement in drilling techniques and proper handling of problem wells can help in reducing the cost and achieving good success. The paper gives a brief over-view of the drilling problems faced over the years in Potwar, hypothesises problems faced over the years in Potwar, hypothesises about the various mechanisms responsible for these high pressures, discusses the utility and limitations of various techniques used for predictability of high pressure zones and, for predictability of high pressure zones and, for the benefit of readers, details the various measures taken to overcome the drilling problems. P. 213
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.51)
- Geology > Structural Geology > Tectonics (0.48)
- Geology > Geological Subdiscipline (0.47)
- Asia > Pakistan > Upper Indus Basin > Potwar Basin (0.99)
- Asia > Pakistan > Punjab > Upper Indus Basin > Potwar Basin > Khaur Field (0.99)
- Asia > Pakistan > Punjab > Upper Indus Basin > Potwar Basin > Dhulian Field > Chorgali-Sakesar Formation (0.99)
- (2 more...)
Understanding Source of Produced Water with Varying Salinities in Oil and Gas Field of Eastern Potwar, A Case Study
Khanam, Mehwish (Pakistan Petroleum Limited, Islamabad, Pakistan) | Javed, Waqar Ali (Pakistan Petroleum Limited, Islamabad, Pakistan) | Nazeer, Adeel (Pakistan Petroleum Limited, Islamabad, Pakistan) | Daud, Farrukh (Pakistan Petroleum Limited, Islamabad, Pakistan) | Ashraf, Zaid (Oil and Gas Development Company Limited, Islamabad, Pakistan) | Wahid, Farhan (Oil and Gas Development Company Limited, Islamabad, Pakistan) | Ali, Shahzad (Pakistan Oilfields Limited, Islamabad, Pakistan)
Abstract X field is producing water along with hydrocarbon from Tobra, Khewra & Sakesar reservoirs. Hence, it is imperative to understand the source of this water and its entry into the wells to optimize the field's production and limit the water production within the available water handling and disposal constraints. Even though multiple wells have been drilled in the field to-date, depth of the free water level is still unknown in the Tobra and Khewra formations. Large uncertainty lies with the thickness of the transition zone across the reservoirs with permeabilities ranging from 4 to 10 md. Besides, capillary forces are likely to have some effect in the rise of water in the pore space leading to some water production. In context of the uncertainties associated with the water breakthrough time and predicting the trend of water cut, it is considered useful to investigate the source of water via the information on the salinities and ion analyses. Four types of water have been produced from four types of reservoir rocks. Water ranges from fresh to brackish, and brackish to brine. Murree Formation is producing freshwater on surface; and hydrocarbon (HC) shows during drilling. Water production in Sakesar is high with relatively less salinity and high pressures. Surface Well Testing (SWT) data confirmed the water salinity of brine origin with varying composition. Sakesar formation's water salinity in X field ranges between 10,000 - 20,000 ppm is because of fresh water mixing with marine origin. However, nearby regional produced water salinity is 50,000 - 60,000 ppm from Sakesar. SWT data showed the production of high saline water in Tobra and Khewra reservoirs. However, salinity greater than 80,000 ppm is not associated with depositional environment of glacial sands (Tobra), and deltaic sands (Khewra); nor present in present day oceans and seas. Probably high saline water (brine) encroached in the formation from somewhere else. Our research is based on the chemical testing of water samples collected during well testing campaigns. Data was analyzed to understand the origin of water in Potwar Plateau, X field and probable ranges of salinity in different depositional environment. This case study is focused on the source of water from underlying formations or through deep seated faults. Same will be confirmed by detailed evaluation of SWT data and water analyses. In this paper, water breakthrough will be discussed with varying salinities in different wells depending upon the faults in the vicinity.
- Asia > Pakistan (0.73)
- North America > United States > Texas (0.47)
- Phanerozoic > Paleozoic (1.00)
- Phanerozoic > Cenozoic (0.95)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.48)
- Geology > Sedimentary Geology > Depositional Environment > Continental Environment > Glacial Environment (0.35)
- North America > United States > Texas > Frio Formation (0.99)
- Europe > France > Paris Basin > Chaunoy Formation (0.99)
- Asia > Pakistan > Upper Indus Basin > Potwar Basin (0.99)
- Asia > Pakistan > Punjab > Chakwal District > Upper Indus Basin > Potwar Basin > Sakesar Formation (0.99)