1、Drilling Ahead Safely with Lost Circulation in the Gulf of MexicoAPI BULLETIN 92LFIRST EDITION, AUGUST 2015Special NotesAPI publications necessarily address problems of a general nature. With respect to particular circumstances, local,state, and federal laws and regulations should be reviewed.Neithe
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4、one desiring to do so. Every effort has been made by the Institute to assure theaccuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, orguarantee in connection with this publication and hereby expressly disclaims any liability or responsibi
5、lity for loss ordamage resulting from its use or for the violation of any authorities having jurisdiction with which this publication mayconflict.API publications are published to facilitate the broad availability of proven, sound engineering and operatingpractices. These publications are not intend
6、ed to obviate the need for applying sound engineering judgmentregarding when and where these publications should be utilized. The formulation and publication of API publicationsis not intended in any way to inhibit anyone from using any other practices.Any manufacturer marking equipment or materials
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9、itted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005.Copyright 2015 American Petroleum InstituteForewordNothing contained in any
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14、enerally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-timeextension of up to two years may be added to this review cycle. Status of the publication can be ascertained from theAPI Standards Department, telephone (202) 682-8000. A catalog of API pu
15、blications and materials is publishedannually by API, 1220 L Street, NW, Washington, DC 20005.Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW,Washington, DC 20005, standardsapi.org.iiiContentsPage1 Scope . . . . . . . . . . . . . . . . . .
16、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Terms and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Backgro
17、und . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18、 . . . . . . . . . . . . . . . . 53.2 Lost Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.3 Mud Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.4 Drilling Margin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.5 Calculating Equivalent Circulating Density (ECD). .
20、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Decision Tree Flow Charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Solutions. . . . . . . . . . . . . . . . . . . .
21、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Figur
22、es1 Drilling Exploration Wells with Lost Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 Drilling Ahead below Salt with Lost Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Drilli
23、ng Depleted Zones with Lost Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Managed Pressure Drilling with Lost Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12vIntroductionLost ci
24、rculation during drilling operations, in the form of both seepage and fracture losses, is a common occurrence inthe Gulf of Mexico (GoM) and other Outer Continental Shelf (OCS) environments. Through extensive practicalexperience, operators and drilling contractors have learned that with proper infor
25、mation, planning and execution, lostcirculation can be safely managed to allow well construction goals to be met. The methods used to repair or managelost circulation are based on well location, geology, pore and fracture pressures, drilling depth, well design, hydraulics,mud properties, and availab
26、le contingencies.vi1 Drilling Ahead Safely with Lost Circulation in the Gulf of Mexico 1 Scope This bulletin identifies items that should be considered to safely address lost circulation challenges when the equivalent circulating density (ECD) exceeds the fracture gradient. It addresses drilling mar
27、gins and drilling ahead with mud losses, which are not addressed in API 65-2. It provides guidance when lost circulation is experienced with either surface or subsea stack operations (excluding diverter operations). These practices may apply to other Outer Continental Shelf (OCS) environments such a
28、s offshore California and Florida. 2 Terms and Definitions For the purposes of this document, the following definitions apply. 2.1 abnormal pressure Pressures greater than normal pressure, i.e. formation pressure that exceeds the gradient of a continuous column of water terminating at the surface or
29、 the seafloor. NOTE Normal pressure in the GoM region is commonly considered to have gradients in the range of 8.65 ppg to 9.0 ppg. Abnormal pressure has a higher gradient. 2.2 annulus friction pressure PaThe steady state circulating pressure loss of a cuttings free fluid occurring within the drill
30、string and casing and/or open-hole annulus. NOTE The term does not include pressure effects associated with cuttings loading. 2.3 application for permit to modify/revised permit to drill APM/RPD This document requests changes to a well permit. NOTE This regulatory submittal document can require a ri
31、sk assessment and/or procedures for the changes to be approved. 2.4 ballooning (wellbore breathing) The event in which fluid is lost to the formation while circulating and flows back into the wellbore when circulation is stopped. NOTE 1 During ballooning, mud returns will be at a steady or decreasin
32、g rate over time. NOTE 2 Increasing return rates are not expected with ballooning and would be an indication of the influx of formation fluids. NOTE 3 Return volumes are expected to be limited to the volume lost to the formation. 2.5 depleted zone A geologic interval having a pore pressure lower tha
33、n the original reservoir pressure caused by production from that interval. NOTE The reduction in pore pressure can create a lower fracture pressure within the interval. 2 API BULLETIN 92L 2.6 development well A well that is drilled to provide additional access to known hydrocarbon resources. NOTE In
34、 a development drilling scenario, geological information (e.g. stratigraphic and geo-pressure) is often available from nearby wells. 2.7 downhole mud weight DHMW The static mud weight (expressed in ppg) that exists in the well, accounting for mud compressibility and thermal effects that can increase
35、 or decrease the value from the surface mud weight. NOTE 1 This term does not include the contribution to the effective fluid density caused by drill cuttings load. When the DHMW has the cuttings load included, it becomes the ESD. NOTE 2 Downhole mud weight can be estimated with mud hydraulics progr
36、ams and can be measured with pressure while drilling (PWD) when drill cuttings are not present. NOTE 3 The downhole static pressure can be measured with PWD prior to drilling the shoe (when the mud is without a cuttings load) to establish a baseline value for mud static density. 2.8 drilling Activit
37、ies that increase the measured depth of the well (this does not include reaming, tripping, circulating, running casing, blowout preventer testing, cementing, hole enlargement, etc.). 2.9 drilling margin The difference between the lowest estimated fracture gradient (ppg) at a given depth in the open-
38、hole interval (including at the casing shoe) and the drilling fluid density (ppg). NOTE 1 In API 96 the drilling margin is defined as the difference between the maximum pore pressure and the minimum effective fracture pressure. NOTE 2 Cuttings load should not be included when using downhole mud weig
39、ht for drilling margin calculations. 2.10 equivalent circulating density ECD The effective density of the drilling fluid in the annulus while circulating, including the frictional pressure drop in the annulus and the effect of cuttings load above any point of interest. 2.11 equivalent static density
40、 ESD The effective mud weight consisting of the surface mud weight accounting for mud compressibility and thermal effects plus drill cuttings load. NOTE ESD = DHMW + CL 2.12 exploration well A well without a direct offset, not having the geologic information and control (e.g. stratigraphic or geo-pr
41、essure information) that would typically be available from a nearby well. DRILLING AHEAD SAFELY WITH LOST CIRCULATION IN THE GULF OF MEXICO 3 2.13 fingerprinting The characterization of the volume and rate of fluid flow back to the pit system from the wellbore and the surface circulating system (as
42、a function of time) after the pumps are shut down. NOTE A characteristic flowback response (historical trend) is established for use in distinguishing normal flow back trends from a wellbore influx (i.e., kick). 2.14 formation integrity test (FIT) A test conducted to a pre-determined pressure to con
43、firm the minimum pressure capacity of the open-hole formation and the cemented annular barrier at the casing shoe, commonly expressed in equivalent mud weight (ppg). NOTE This test is done after drilling 10 ft to 50 ft (3 m to 15 m) of new formation below a cemented casing. A FIT is considered an op
44、en-hole FIT if conducted after drilling more than 50 ft (15 m) of new formation. 2.15 fracture gradient The pressure required to create fracture growth in rock at a given depth, commonly expressed in equivalent mud weight. 2.16 leak-off test LOT A test conducted to a pressure that initiates a fractu
45、re in an open-hole formation and thus determines the fracture gradient (i.e. integrity) in the vicinity of the cemented casing shoe. NOTE 1 LOTs can be affected by formation permeability, hole deviation, and temperature. NOTE 2 A LOT is considered an open-hole LOT if conducted after drilling 50 ft (
46、15 m) of new formation. 2.17 lost circulation When drilling fluid flows into geological formations instead of returning up the annulus. NOTE Lost circulation includes seepage, partial, severe, or complete loss of returns during well operations. 2.18 lost returns The loss of whole drilling fluid into
47、 the formation. 2.19 low integrity zone (i.e. rubble zone) below salt Interval below salt that can be mechanically unstable, outside of the normal geological sequence, and potentially a loss zone. 2.20 managed pressure drilling MPD Adaptive drilling process used to control the annular pressure profi
48、le using a combination of fluid density and surface pressure or fluid column height. 2.21 minimum required mud volume The minimum required usable volume that permits three circulations (two for surface stack rigs) of the wellbore excluding the marine riser at the expected/actual lost circulation rat
49、e when drilling ahead while experiencing partial or severe loss of returns. 4 API BULLETIN 92L NOTE 1 This volume can include mud that is available from surface pits (both active and reserve) and the mud on boats at the rig site. NOTE 2 The volume is calculated by multiplying expected/actual lost circulation rate by circulation time. 2.22 normal pressure Equivalent to the density of formation water. NOTE Typically 8.65 ppg to 9.0 ppg for a GoM environment. 2.23 partial returns A portion of the drilling fluid is lost downhole when circulating the well. NOTE 1 The returns are less than the
