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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 184817, “Optimal Production Metric To Predict Unconventional Wells’ Long-Term Performance,” by Edward Ifejika, Bertrand De Cumont, and Nommie Kashani, Total, prepared for the 2017 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, 24–26 January. The paper has not been peer reviewed.
In unconventional plays, comparing the effect of different completion designs or well-management strategies on well performance remains a challenge because of the relatively brief production history and lack of long-term field analogs of these plays. This study examines various production durations as potential candidates for reliable indicators of well quality. The results show that predictions of midterm performance begin to be reliable only near 180 days of cumulative well production. This study used actual daily production data to confirm that 30- and 90-day initial production are not correlated strongly to well actual performance in the 2-year range.
It has been a common practice to quantify performance of unconventional wells through their 30-day initial production for purposes of information for the media and in investor presentations. The authors’ experience has been that the 30-day initial production often does not necessarily quantify a well’s potential. The goal of this study is to compare various production-duration periods to identify which can most accurately forecast longer-term production. This study tests different production durations by use of actual well-production history from the Utica play in Ohio, USA. The term “IP-nnn” in the paper refers to a specific number of days of nonzero production for the well; for example, “wellhead gas IP-30” refers to the total volume of the first 30 days of nonzero wellhead gas production for the well, whereas “condensate IP-90” refers to the total volume of the first 90 days of nonzero condensate production for the well.
Study Description and Assumptions
A data set of 676 unconventional producing wells for the Utica play was used to conduct this study. The authors began the study with several assumptions based on anecdotal observations from the early days of production in the play, with the goal of eventually using this data set to test the accuracy of their assumptions, which were as follows:
Donovan, Glenn (Shell Exploration and Production Co.) | Kamath, Sagar (Shell Exploration and Production Co.) | Tanis, Elizabeth (Shell Exploration and Production Co.) | Abbassi, Linda (Openfield Technology) | Gysen, Alain (Interpretive Software Products)
This paper discusses the effectiveness of the third-generation (Gen3) Production Logging Tool (PLT) technology which incorporates the use of co-located digital sensors for simultaneous acquisition of flow data. Case studies are provided which demonstrate that this technology is a step-change in the application of digitalization to a down-hole sensor platform which provides the most accurate characterization of the flow condition at each depth surveyed. The resulting data allows for much improved processing which is also described. The probabilistic interpretive model used in the processing has been updated to incorporate this and future developments in PLT architecture.
Planning, execution, and analysis of data for the wells is described in detail. Due to the significantly shorter configuration of Gen3 tools, safety at the wellsite is enhanced by allowing for a much-simplified surface rig-up. One well was logged in surface readout (SRO) mode while data in the other two were recorded in the downhole tool's memory for retrieval at the surface at the end of operations. This flexibility in logging modes optimizes operations by addressing the needs of the operation teams.
Three Deepwater Gulf of Mexico producers logged with the Gen3 PLT are described. In each case, a clear path forward is provided for optimal management of the reservoirs through effective production management.
The first generation (Gen1) of PLT provided a single discrete measurement for each sensor along the tool assembly's length, resulting in long tool assemblies and measurements taken at different points along the flow path. This approach had several drawbacks: long toolstrings, point sensors only provided a measurement at a single point in the cross-section of the flow, and measurements were not acquired simultaneously at each depth logged. The second generation (Gen2) of PLT was an improvement as sensors were arranged as an array enabling multiple measurements to be made at a single depth but were still long and not all were optimally arranged to capture data in the path of flow. The Gen3 PLT is one-tenth the length of the Gen1 versions and roughly one-third of the shortest Gen2 tools. Digitization allows for direct measurement of flow conditions and rapid interpretation of results. In multi-phase flow and deviated wells, the co-location of sensors in a spatial geometry provides the optimal information with which to create a fully accurate picture of the downhole flow.
In unconventional plays, comparing the effect of different completion designs or well-management strategies on well performance remains a challenge because of the relatively brief production history and lack of long-term field analogs of these plays. This study examines various production durations as potential candidates for reliable indicators of well quality. The results show that predictions of midterm performance begin to be reliable only near 180 days of cumulative well production. This study used actual daily production data to confirm that 30- and 90-day initial production are not correlated strongly to well actual performance in the 2-year range. It has been a common practice to quantify performance of unconventional wells through their 30-day initial production for purposes of information for the media and in investor presentations.
During the past 98 years the United States has produced annually more crude oil than any other country, except during one three-year period and another period of four years. Needless to say this nation has surpassed all others in cumulative production.
The United States for many years has produced a greater percentage of its proved reserves annually than has any other country with large reserves. The high annual withdrawal from reserves by this nation in the past may lead in the future to the loss of its status as center of crude oil production.
Center of Annual Production
Rumania, birthplace of the oil industry, was the center of crude oil production during the three-year period, 1857 to 1859 (Fig. 1 and Table 1). Actually, it had the only recorded output in 1857 and 1858 and 67 per cent of world production in 1859. Before continuing the citation of honors as center of world's production, it should be mentioned that there may have been small production from some spot before records were kept.
The United States was largest producer from 1860 through 1897. U.S.S.R. took the lead from this nation in 1898 and held it through 1901. However, the United States regained the front position in 1902 and has not been overtaken since then. Since the first year of its supremacy, 1860, the United States has produced 50 per cent or more of world's production every year with these exceptions: 1898 to 1902, inclusive, 1953 and 1954. During the period 1907 through 1947 thenation's output was over 60 per cent of world's production each year, and in six of the years it produced 70 per cent or more of world's total.
There are several countries that should not be ignored despite the fact that they have not led the world as yet in production any year. A comparison of the maximum annual production of each of nine countries and the same year's production of the other eight countries is shown in Table 2. (See Fig. 2 also.) Six of the cited countries registered their maximum annual production in 1954. Probably all of these could produce more than they did in 1954. The percentage of the world's 1954 production credited to Iraq, Kuwait, and Saudi Arabia - and the known potentialities of these countries and Iran - suggest the direction in which the center of production is moving.