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Du, Qizhen (School of Geosciences, China University of Petroleum-East China) | Yasin, Qamar (School of Geosciences, China University of Petroleum-East China) | Ismail, Atif (Department of Geological Engineering, University of Engineering and Technology Lahore, Pakistan)
Verifiable and accurate estimation of shear wave velocity (VS) in a well with no previous exposure of velocity profile is the bottom line for any technique to declare the VS estimation capabilities. So far all the available models and techniques for VS estimation have been attempted on well logs and laboratory based core measurements. This study aims to compare the role of virtual measurement using Artificial Neural Network (ANN) and rock physics analysis using Gassmann equation for the estimation of VS in a highly heterogeneous reservoir. The techniques were applied initially to the well containing specialized logging and laboratory analysis data and prediction of VS models were developed. The developed model was then applied to the offset well whose data was not included in the model development and the results were compared with measured VS data. The results show that although rock physics model provides acceptable results that show consistency in following the actual trend in shear and compressional wave velocities estimation it lacks a consistent generalization power, meaning that it does not work as well with the data of unstable zones. On the other hand, ANN provides more realistic results because of its discriminatory power and observe the actual trend in VS estimation even at unstable zones.
Presentation Date: Wednesday, October 17, 2018
Start Time: 9:20:00 AM
Location: Poster Station 1
Presentation Type: Poster
Sand control techniques are widely used in industry to prevent sand production. However these techniques significantly increase completion cost and complexity as well as can potentially impact production and field economics. Hence it is preferred not to install sand control if one can be assured that the sand volume which will be produced is manageable. However, there are no tools or workflows which can consistently and accurately predict the expected sand volume and timing over the life of the field without a large range of uncertainty.
In this study, sand production characteristics were tested in three different sandstone outcrops under varying fluid flow conditions. The test results show different sanding behavior for brine, oil, and gas flow. Samples tested with brine fail catastrophically when stress is applied which slightly exceeds the onset of sand production stress. Samples with gas flow produce small amounts of sand even when the stress significantly exceeds the onset of sand production. The test results also demonstrated the importance of drawdown pressure on sand production, where an increase in drawdown has the potential to significantly increase the sand production. Subsequently both numerical and empirical models were developed to estimate and predict sand production volume. These models have been able to model field sand production cases reasonably well
Risk of sand production is considered to be a major economic and technical issue in field developments with large expected drawdowns, depletion or relatively unconsolidated rock. Unnecessary sand control leads to expensive completions and potentially high skins which can result in lower productivity and poor recovery. However, inadequate sand control may lead to sand production problems. The produced sand can erode and damage downhole and surface equipment, including downhole pumps, chokes and flowlines. Produced sand may also fill the wellbore, restrict production, and require costly workovers and cleanup operations.
Historically, downhole sand control equipment is installed to eliminate sand production from these formations. As reserves are discovered in ever more challenging environments, such as deep water, heavy oil, and high-pressure/high-temperatures, well completions are required to balance multiple conflicting operational and business drivers. Traditional downhole sand control methods can significantly increase the complexity and cost of the completions which can challenge the field development economics. For these reasons, allowing some sand production and managing sand on surface has gained momentum in recent years [1-3].
In order to manage sand on surface, predicting the onset of sand production is not sufficient. Significant effort in the industry has been focused on modeling the evolution of sand production with time both experimentally and theoretically [4-9]. Sand production is a complex process. Sand production rate and volume are not controlled only by geomechanical factors, such as rock strength and stresses, but are also influenced by hydrodynamic processes. Reservoir depletion, changing production rate, increasing water cut, and changing gas-oil ratio over the well life all influence the sand production rate and volume. Therefore modeling and predicting sand production rate and volume over time is much more problematic than predicting the onset of sand production.
Widening supply and demand gap in natural gas industry, the advent of tight gas policy and increasing interest of operators in tight gas sands and shale has opened new venues for development of unconventional plays in Pakistan.
Middle Indus Basin hosts important gas fields of Pakistan. Most of the wells in this basin are completed in conventional lower Goru Sands. Lower Goru formation consists of inter-bedded sequences of sands and shale. Its unconventional sand and shale plays hold immense potential which has not yet been exploited due to lack of technology and promising economics. Moreover, Sembar shale is the well known source rock in this basin holding large shale gas potential. GIIP estimates for Lower Goru tight sands excluding the shale prospects are 8.4 TCF which are considered pessimistic due to lack of data in many fields.
From the currently suspended or abandoned wellbores of the Middle Indus Basin, a pilot project needs to be defined in each of the fields, to prove the technical and economical feasibility of tight Gas Potential of the Basin. Commencement of production from unconventional sands will enhance the production in a cost effective manner due to availability of infrastructure and facilities.
This paper focuses on the utilization of existing wellbores as well as data set and highlighting additional data acquisition requirements coupled with completion and multi-stage fracturing techniques for designing a pilot project. Case study of a pilot project in one of the fields of this basin is discussed. It encompasses the basic workflow, candidate selection criterion, Geo-mechanics, sector modeling, hydraulic fracture design and risk evaluation coupled with its use in full field development projects.
Background and Introduction
Pakistan's last year 2010-2011 production was about 3.91bcf/d, while its demand was (4.2bcf/d) and supply gap was also started. Since then the production from the conventional fields has decreased, while demand has been increased due to infrastructure and human needs. This huge shortfall in the gas market cannot be fulfilled with existing number of completions/producers. The conventional reserves of the country were 56 TCF out of which the country has already produced 50% of its conventional reserves. The recoverable remaining reserves are 24-28TCF, but will be produced at much lower production rate and in much longer period of time. The country has an infrastructure of Gas Processing Facilities 5bcf/d.
Thank you to all section members for attending Distinguished Lecturer meetings and submitting evaluations during the 2011-12 DL season. A new DL season (2012-13) begins in September. Fill out and submit the Section Attendees’ Tour Evaluation form for every DL visit. The President’s Award for Section Excellence recognizes SPE sections who display exemplary efforts in technology dissemination, section operations, member benefits, society and community benefits and innovation. The awards are presented to an officer of each section during the President’s Luncheon at the SPE Annual Technical Conference and Exhibition.
We welcome the following new student chapters to SPE. This year, with more than 400 attendees and 20 student chapters represented, the University of Ibadan emerged as the winner at Petroquiz in Nigeria. Finalists were the University of Port Harcourt, Nnamdi Azikiwe University, Igbinedion University, and the University of Ibadan. ISPC Student Paper Contest 2012 winner, Ogunleye Ayowole, is a bright example of a “Woman in Engineering” who is encouraging female student members. During SPEUI Week, the student chapter reached out to the communities at the Prem Dham Old Age Home and Chechire Home of the Challenged.
SPE Mehran Student Chapter arranged field trips for the final-year students. Mr. Gul Hassan Dars briefed students about the history of the field. Twenty five final-year students also visited the Kadanwaari Gas field. Students visited the sampling laboratory, central control room (CCR) and processing plant. Technical personnel at the field told the students about the plant operation, gas composition and equipment used at the field.
This paper demonstrates an innovative in-situ natural gas lifting approach, which has been successfully applied in AG pool of FN field, Sudan. AG pool is a series of edge water driven stacked sandstones with light oil and natural gas pools, and mostly natural gas zones are below oil zones. AG oil is typical of high pour point, ranging from 37 to 57 Celsius degree. Possibility of wax deposition posed great production and operational challenges at 27 Celsius degree surface temperature. Gas below oil pool could serve as in-situ gas lifting to boost production and reduce wax deposition. This process undergoes tubing produced natural gas flowing simultaneously into annular to lift oil production in the same wellbore. This process has been optimized by following approaches: 1) establishing screening criteria of qualified gas and oil zones for lifting; 2) Partial completion and reduced perforation density in gas zones for controllable gas rate; 3) Separators deployed to remove portion of gas for smooth transportation to facilities.
4 producers have undergone in-situ gas lifting since 2009, average well output achieved 2 to 4 times of DST rate, amounting to 2000 to 4000 BOPD with low water cut. Up-efficiency has been above 85% without wax deposition problems. Operational costs were greatly reduced. Conclusions drawn from successful in-situ gas lifting application were:1) selected oil and gas zones fully qualified for gas lifting; 2) optimized in-situ gas lifting brought high output and low water cut; 3) innovative wellbore structure and facilities design replaced the use of pumps and saved costs.
Sudan is abundant in stacked oil and gas pools with high pour point, therefore in-situ gas lifting has wide applications.
Successful in-situ gas lifting in this paper highlighted significant oil rate gain without oil gelling problems, cost-effective wellbore structure and facilities design, give a staircase for future wider applications.
Heikal, S. (ENI Pakistan Ltd) | Santellani, G. (ENI Pakistan Ltd) | Sultan, A. (ENI Pakistan Ltd) | Mugheri, S. (ENI Pakistan Ltd) | Eisa, H. (ENI Pakistan Ltd) | Iqbal, J. (Sprint Oil & Gas Services)
Cavanna, Giorgio Rocco (Eni E&P) | Caselgrandi, Ernesto (Eni E&P) | Corti, Elisa (Eni Indonesia Ltd) | Amato del Monte, Alessandro (Eni Indonesia Ltd) | Fervari, Massimo (Eni Indonesia Ltd) | Bello, Mario | Aruan, Johnny | Golding, Christopher